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Kiwanuka N, Zalwango S, Kakaire R, Castellanos ME, Quach THT, Whalen CC. M. tuberculosis Infection Attributable to Exposure in Social Networks of Tuberculosis Cases in an Urban African Community. Open Forum Infect Dis 2024; 11:ofae200. [PMID: 38737427 PMCID: PMC11083641 DOI: 10.1093/ofid/ofae200] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2023] [Accepted: 04/11/2024] [Indexed: 05/14/2024] Open
Abstract
Background The persistence of tuberculosis today and its global disparity send a powerful message that effective tuberculosis control must respond to its regional epidemiology. Active case finding through contact investigation is a standard protocol used for tuberculosis control, but its effectiveness has not been established, especially in endemic areas. Methods To quantify the potential effectiveness of contact investigation in Kampala, Uganda, we used a cross-sectional design to evaluate the social networks of 123 tuberculosis index cases and 124 controls without tuberculosis. Results Tuberculous infection was present in 515 of 989 tuberculosis case contacts (52.1%) and 396 of 1026 control contacts (38.6%; adjusted prevalence ratio, 1.4; 95% CI, 1.3-1.6). The proportion of infected participants with known exposure within the social network of the tuberculosis case was 35%. The population-attributable fraction was 11.1% for any known exposure, with 7.3% attributable to household exposure and 3.4% attributable to extrahousehold exposure. Conclusions This low population-attributable fraction indicates that contact tracing in the social networks of index cases will have only a modest effect in reducing tuberculous infection in a community. New approaches to community-level active case finding are needed.
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Affiliation(s)
- Noah Kiwanuka
- Department of Epidemiology and Biostatistics, School of Public Health, College of Health Sciences, Makerere University, Kampala, Uganda
| | - Sarah Zalwango
- Department of Public Health and Environment, Kampala Capital City Authority, Kampala, Uganda
| | - Robert Kakaire
- Global Health Institute, College of Public Health, University of Georgia, Athens, Georgia, USA
| | - Maria Eugenia Castellanos
- Public Health and Tropical Medicine, College of Public Health, Medical and Veterinary Sciences, James Cook University, Townsville, Australia
| | - Trang Ho Thu Quach
- Global Health Institute, College of Public Health, University of Georgia, Athens, Georgia, USA
| | - Christopher C Whalen
- Global Health Institute, College of Public Health, University of Georgia, Athens, Georgia, USA
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Dinkele R, Gessner S, Patterson B, McKerry A, Hoosen Z, Vazi A, Seldon R, Koch A, Warner DF, Wood R. Persistent Mycobacterium tuberculosis bioaerosol release in a tuberculosis-endemic setting. MEDRXIV : THE PREPRINT SERVER FOR HEALTH SCIENCES 2024:2024.04.02.24305196. [PMID: 38633787 PMCID: PMC11023659 DOI: 10.1101/2024.04.02.24305196] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/19/2024]
Abstract
Pioneering studies linking symptomatic disease and cough-mediated release of Mycobacterium tuberculosis (Mtb) established the infectious origin of tuberculosis (TB), simultaneously informing the pervasive notion that pathology is a prerequisite for Mtb transmission. Our prior work has challenged this assumption: by sampling TB clinic attendees, we detected equivalent release of Mtb-containing bioaerosols by confirmed TB patients and individuals not receiving a TB diagnosis, and we demonstrated a time-dependent reduction in Mtb bioaerosol positivity during six-months' follow-up, irrespective of anti-TB chemotherapy. Now, by extending bioaerosol sampling to a randomly selected community cohort, we show that Mtb release is common in a TB-endemic setting: of 89 participants, 79.8% (71/89) produced Mtb bioaerosols independently of QuantiFERON-TB Gold status, a standard test for Mtb infection; moreover, during two-months' longitudinal sampling, only 2% (1/50) were serially Mtb bioaerosol negative. These results necessitate a reframing of the prevailing paradigm of Mtb transmission and infection, and may explain the current inability to elucidate Mtb transmission networks in TB-endemic regions.
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Affiliation(s)
- Ryan Dinkele
- UCT Molecular Mycobacteriology Research Unit, Department of Pathology, Faculty of Health Sciences, University of Cape Town, Cape Town, 7925, South Africa
- Institute of Infectious Disease and Molecular Medicine, Faculty of Health Sciences, University of Cape Town, Cape Town, 7925, South Africa
| | - Sophia Gessner
- UCT Molecular Mycobacteriology Research Unit, Department of Pathology, Faculty of Health Sciences, University of Cape Town, Cape Town, 7925, South Africa
- Institute of Infectious Disease and Molecular Medicine, Faculty of Health Sciences, University of Cape Town, Cape Town, 7925, South Africa
| | - Benjamin Patterson
- Amsterdam Institute for Global Health and Development, University of Amsterdam, Amsterdam, 1105, The Netherlands
| | - Andrea McKerry
- Aerobiology and TB Research Unit, Desmond Tutu Health Foundation, Cape Town, 7925, South Africa
| | - Zeenat Hoosen
- Aerobiology and TB Research Unit, Desmond Tutu Health Foundation, Cape Town, 7925, South Africa
| | - Andiswa Vazi
- Aerobiology and TB Research Unit, Desmond Tutu Health Foundation, Cape Town, 7925, South Africa
| | - Ronnett Seldon
- Aerobiology and TB Research Unit, Desmond Tutu Health Foundation, Cape Town, 7925, South Africa
| | - Anastasia Koch
- UCT Molecular Mycobacteriology Research Unit, Department of Pathology, Faculty of Health Sciences, University of Cape Town, Cape Town, 7925, South Africa
- Institute of Infectious Disease and Molecular Medicine, Faculty of Health Sciences, University of Cape Town, Cape Town, 7925, South Africa
| | - Digby F. Warner
- UCT Molecular Mycobacteriology Research Unit, Department of Pathology, Faculty of Health Sciences, University of Cape Town, Cape Town, 7925, South Africa
- Institute of Infectious Disease and Molecular Medicine, Faculty of Health Sciences, University of Cape Town, Cape Town, 7925, South Africa
- Wellcome Centre for Infectious Diseases Research in Africa, Faculty of Health Sciences, University of Cape Town, Cape Town, 7925, South Africa
| | - Robin Wood
- Institute of Infectious Disease and Molecular Medicine, Faculty of Health Sciences, University of Cape Town, Cape Town, 7925, South Africa
- Aerobiology and TB Research Unit, Desmond Tutu Health Foundation, Cape Town, 7925, South Africa
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Coleman M, Martinez L, Theron G, Wood R, Marais B. Mycobacterium tuberculosis Transmission in High-Incidence Settings-New Paradigms and Insights. Pathogens 2022; 11:1228. [PMID: 36364978 PMCID: PMC9695830 DOI: 10.3390/pathogens11111228] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2022] [Revised: 10/20/2022] [Accepted: 10/21/2022] [Indexed: 12/01/2023] Open
Abstract
Tuberculosis has affected humankind for thousands of years, but a deeper understanding of its cause and transmission only arose after Robert Koch discovered Mycobacterium tuberculosis in 1882. Valuable insight has been gained since, but the accumulation of knowledge has been frustratingly slow and incomplete for a pathogen that remains the number one infectious disease killer on the planet. Contrast that to the rapid progress that has been made in our understanding SARS-CoV-2 (the cause of COVID-19) aerobiology and transmission. In this Review, we discuss important historical and contemporary insights into M. tuberculosis transmission. Historical insights describing the principles of aerosol transmission, as well as relevant pathogen, host and environment factors are described. Furthermore, novel insights into asymptomatic and subclinical tuberculosis, and the potential role this may play in population-level transmission is discussed. Progress towards understanding the full spectrum of M. tuberculosis transmission in high-burden settings has been hampered by sub-optimal diagnostic tools, limited basic science exploration and inadequate study designs. We propose that, as a tuberculosis field, we must learn from and capitalize on the novel insights and methods that have been developed to investigate SARS-CoV-2 transmission to limit ongoing tuberculosis transmission, which sustains the global pandemic.
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Affiliation(s)
- Mikaela Coleman
- WHO Collaborating Centre for Tuberculosis and the Sydney Institute for Infectious Diseases, The University of Sydney, Sydney 2006, Australia
- Tuberculosis Research Program, Centenary Institute, The University of Sydney, Sydney 2050, Australia
| | - Leonardo Martinez
- Department of Epidemiology, Boston University School of Public Health, Boston, MA 02118, USA
| | - Grant Theron
- DSI-NRF Centre of Excellence for Biomedical Tuberculosis Research, South African Medical Research Council Centre for Tuberculosis Research, Division of Molecular Biology and Human Genetics, Faculty of Medicine and Health Sciences, Stellenbosch University, Cape Town 7602, South Africa
| | - Robin Wood
- Desmond Tutu Health Foundation and Institute of Infectious Disease and Molecular Medicine, University of Cape Town, Cape Town 7700, South Africa
| | - Ben Marais
- WHO Collaborating Centre for Tuberculosis and the Sydney Institute for Infectious Diseases, The University of Sydney, Sydney 2006, Australia
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Khundi M, Carpenter JR, Nliwasa M, Cohen T, Corbett EL, MacPherson P. Effectiveness of spatially targeted interventions for control of HIV, tuberculosis, leprosy and malaria: a systematic review. BMJ Open 2021; 11:e044715. [PMID: 34257091 PMCID: PMC8278879 DOI: 10.1136/bmjopen-2020-044715] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/16/2020] [Accepted: 06/15/2021] [Indexed: 11/12/2022] Open
Abstract
BACKGROUND As infectious diseases approach global elimination targets, spatial targeting is increasingly important to identify community hotspots of transmission and effectively target interventions. We aimed to synthesise relevant evidence to define best practice approaches and identify policy and research gaps. OBJECTIVE To systematically appraise evidence for the effectiveness of spatially targeted community public health interventions for HIV, tuberculosis (TB), leprosy and malaria. DESIGN Systematic review. DATA SOURCES We searched Medline, Embase, Global Health, Web of Science and Cochrane Database of Systematic Reviews between 1 January 1993 and 22 March 2021. STUDY SELECTION The studies had to include HIV or TB or leprosy or malaria and spatial hotspot definition, and community interventions. DATA EXTRACTION AND SYNTHESIS A data extraction tool was used. For each study, we summarised approaches to identifying hotpots, intervention design and effectiveness of the intervention. RESULTS Ten studies, including one cluster randomised trial and nine with alternative designs (before-after, comparator area), satisfied our inclusion criteria. Spatially targeted interventions for HIV (one USA study), TB (three USA) and leprosy (two Brazil, one Federated States of Micronesia) each used household location and disease density to define hotspots followed by community-based screening. Malaria studies (one each from India, Indonesia and Kenya) used household location and disease density for hotspot identification followed by complex interventions typically combining community screening, larviciding of stagnant water bodies, indoor residual spraying and mass drug administration. Evidence of effect was mixed. CONCLUSIONS Studies investigating spatially targeted interventions were few in number, and mostly underpowered or otherwise limited methodologically, affecting interpretation of intervention impact. Applying advanced epidemiological methodologies supporting more robust hotspot identification and larger or more intensive interventions would strengthen the evidence-base for this increasingly important approach. PROSPERO REGISTRATION NUMBER CRD42019130133.
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Affiliation(s)
- McEwen Khundi
- Public Health, Malawi-Liverpool-Wellcome Trust Clinical Research Programme, Blantyre, Malawi
- Medical Statistics, London School of Hygiene and Tropical Medicine, London, UK
| | - James R Carpenter
- Medical Statistics, London School of Hygiene and Tropical Medicine, London, UK
- MRC Clinical Trials Unit, University College London, London, UK
| | - Marriott Nliwasa
- Helse Nord Tuberculosis Initiative, University of Malawi College of Medicine, Blantyre, Malawi
| | - Ted Cohen
- School of Public Health, Yale University, New Haven, Connecticut, USA
| | - Elizabeth L Corbett
- Public Health, Malawi-Liverpool-Wellcome Trust Clinical Research Programme, Blantyre, Malawi
- Department of Clinical Research, London School of Hygiene & Tropical Medicine, London, UK
| | - Peter MacPherson
- Public Health, Malawi-Liverpool-Wellcome Trust Clinical Research Programme, Blantyre, Malawi
- Medical Statistics, London School of Hygiene and Tropical Medicine, London, UK
- Department of Clinical Sciences, Liverpool School of Tropical Medicine, Liverpool, UK
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Horton KC, Hoey AL, Béraud G, Corbett EL, White RG. Systematic Review and Meta-Analysis of Sex Differences in Social Contact Patterns and Implications for Tuberculosis Transmission and Control. Emerg Infect Dis 2021; 26:910-919. [PMID: 32310063 PMCID: PMC7181919 DOI: 10.3201/eid2605.190574] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Social contact patterns might contribute to excess burden of tuberculosis in men. We conducted a study of social contact surveys to evaluate contact patterns relevant to tuberculosis transmission. Available data describe 21 surveys in 17 countries and show profound differences in sex-based and age-based patterns of contact. Adults reported more adult contacts than children. Children preferentially mixed with women in all surveys (median sex assortativity 58%, interquartile range [IQR] 57%–59% for boys, 61% [IQR 60%–63%] for girls). Men and women reported sex-assortative mixing in 80% and 95% of surveys (median sex assortativity 56% [IQR 54%–58%] for men, 59% [IQR 57%–63%] for women). Sex-specific patterns of contact with adults were similar at home and outside the home for children; adults reported greater sex assortativity outside the home in most surveys. Sex assortativity in adult contacts likely contributes to sex disparities in adult tuberculosis burden by amplifying incidence among men.
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Transmission Modeling with Regression Adjustment for Analyzing Household-based Studies of Infectious Disease: Application to Tuberculosis. Epidemiology 2021; 31:238-247. [PMID: 31764276 DOI: 10.1097/ede.0000000000001143] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
BACKGROUND Household contacts of people infected with a transmissible disease may be at risk due to this proximate exposure, or from other unobserved sources. Understanding variation in infection risk is essential for targeting interventions. METHODS We develop an analytical approach to estimate household and exogenous forces of infection, while accounting for individual-level characteristics that affect susceptibility to disease and transmissibility. We apply this approach to a cohort study conducted in Lima, Peru, of 18,544 subjects in 4,500 households with at least one active tuberculosis (TB) case and compare the results to those obtained by Poisson and logistic regression. RESULTS HIV-coinfected (susceptibility hazard ratio [SHR] = 3.80, 1.56-9.29), child (SHR = 1.72, 1.32-2.23), and teenage (SHR = 2.00, 1.49-2.68) household contacts of TB cases experience a higher hazard of TB than do adult contacts. Isoniazid preventive therapy (SHR = 0.30, 0.21-0.42) and Bacillus Calmette-Guérin (BCG) vaccination (SHR = 0.66, 0.51-0.86) reduce the risk of disease among household contacts. TB cases without microbiological confirmation exert a smaller hazard of TB among their close contacts compared with smear- or culture-positive cases (excess hazard ratio = 0.88, 0.82-0.93 for HIV- cases and 0.82, 0.57-0.94 for HIV+ cases). The extra household force of infection results in 0.01 (95% confidence interval [CI] = 0.004, 0.028) TB cases per susceptible household contact per year and the rate of transmission between a microbiologically confirmed TB case and susceptible household contact at 0.08 (95% CI = 0.045, 0.129) TB cases per pair per year. CONCLUSIONS Accounting for exposure to infected household contacts permits estimation of risk factors for disease susceptibility and transmissibility and comparison of within-household and exogenous forces of infection.
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Martinez L, Woldu H, Chen C, Hallowell BD, Castellanos ME, Lu P, Liu Q, Whalen CC, Zhu L. Transmission Dynamics in Tuberculosis Patients with Human Immunodeficiency Virus: A Systematic Review and Meta-Analysis of 32 Observational Studies. Clin Infect Dis 2020; 73:e3446-e3455. [PMID: 32770236 DOI: 10.1093/cid/ciaa1146] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2020] [Indexed: 11/14/2022] Open
Abstract
BACKGROUND There are large knowledge gaps on the transmission dynamics of Mycobacterium tuberculosis in settings where both tuberculosis and HIV are endemic. We aimed to assess the infectiousness of tuberculosis patients coinfected with HIV. METHODS We systematically searched for studies of contacts of both HIV-positive and negative tuberculosis index cases. Our primary outcome was Mycobacterium tuberculosis infection in contacts. Data on sputum smear and lung cavitation status of index cases was extracted from each study to assess effect modification. Secondary outcomes included prevalent tuberculosis and HIV in contacts of HIV-positive and negative index cases. RESULTS Of 5,255 original citations identified, 32 studies met inclusion criteria including 25 studies investigating M. tuberculosis infection (Nparticipants=36,893), 13 on tuberculosis (Nparticipants=18,853), and 12 on HIV positivity (Nparticipants=18,424). Risk of M. tuberculosis infection was lower in contacts of HIV-positive index cases (Odds Ratio [OR], 0.67, 95% CI, 0.58-0.77) but was heterogeneous (I2=75.1%). Two factors modified this relationship: the lung cavitary status of the index case and immunosuppression (measured through CD4 counts or HIV or AIDS diagnoses) among index patients living with HIV. Rates of HIV were consistently higher in contacts of coinfected index cases (OR, 4.9, 95% CI, 3.0-8.0). This was modified by whether the study was in sub-Saharan Africa (OR, 2.8, 1.6-4.9) or in another global region (OR, 9.8, 5.9-16.3). CONCLUSIONS Tuberculosis patients coinfected with HIV are less infectious than HIV-uninfected cases when they have severe immunosuppression or paucibacillary disease. Contacts of coinfected index cases are almost five times more likely to also have HIV.
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Affiliation(s)
- Leonardo Martinez
- Department of Epidemiology and Biostatistics, College of Public Health, University of Georgia, Athens, Georgia, United States.,Center for Global Health, College of Public Health, University of Georgia, Athens, Georgia, United States.,Stanford University, School of Medicine, Division of Infectious Diseases and Geographic Medicine, Stanford, USA
| | - Henok Woldu
- Biostatistics & Research Design Unit School of Medicine, University of Missouri-Columbia, Columbia, Missouri
| | - Cheng Chen
- Department of Chronic Communicable Disease, Center for Disease Control and Prevention of Jiangsu Province, Nanjing, Jiangsu Province, People's Republic of China.,Key Laboratory of Public Health Safety, Fudan University, Ministry of Education, Shanghai, China.,School of Public Health, Fudan University, Shanghai, China
| | - Benjamin D Hallowell
- Department of Epidemiology and Biostatistics, College of Public Health, University of Georgia, Athens, Georgia, United States.,Center for Global Health, College of Public Health, University of Georgia, Athens, Georgia, United States
| | - Maria Eugenia Castellanos
- Department of Epidemiology and Biostatistics, College of Public Health, University of Georgia, Athens, Georgia, United States.,Center for Global Health, College of Public Health, University of Georgia, Athens, Georgia, United States
| | - Peng Lu
- Department of Chronic Communicable Disease, Center for Disease Control and Prevention of Jiangsu Province, Nanjing, Jiangsu Province, People's Republic of China
| | - Qiao Liu
- Department of Chronic Communicable Disease, Center for Disease Control and Prevention of Jiangsu Province, Nanjing, Jiangsu Province, People's Republic of China
| | - Christopher C Whalen
- Department of Epidemiology and Biostatistics, College of Public Health, University of Georgia, Athens, Georgia, United States.,Center for Global Health, College of Public Health, University of Georgia, Athens, Georgia, United States
| | - Limei Zhu
- Department of Chronic Communicable Disease, Center for Disease Control and Prevention of Jiangsu Province, Nanjing, Jiangsu Province, People's Republic of China
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Patterson B, Koch A, Gessner S, Dinkele R, Gqada M, Bryden W, Cobelens F, Little F, Warner DF, Wood R. Bioaerosol sampling of patients with suspected pulmonary tuberculosis: a study protocol. BMC Infect Dis 2020; 20:587. [PMID: 32770954 PMCID: PMC7414552 DOI: 10.1186/s12879-020-05278-y] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2020] [Accepted: 07/20/2020] [Indexed: 12/20/2022] Open
Abstract
BACKGROUND Tuberculosis (TB) is transmitted in bioaerosols containing Mycobacterium tuberculosis (Mtb). Despite being central to ongoing TB transmission, no routine diagnostic assay exists to measure Mtb in bioaerosols. Furthermore, published studies of Mtb in bioaerosol samples have been limited to individuals with sputum-positive pulmonary TB. Notably, TB diagnosis is based on clinical symptoms and sputum laboratory findings. This is despite the fact that approximately half of all patients commencing TB treatment are sputum-negative, resulting in a high proportion of presumptive treatments. Here, we propose to use a sensitive air sampling protocol to investigate the prevalence of Mtb-containing bioaerosols in both sputum-positive and sputum-negative TB suspects, at the same time evaluating the potential to identify unrecognized transmitters of TB. METHODS Our parallel-group design will identify viable Mtb in bioaerosols produced by individuals attending a TB clinic in South Africa. Sampling will be performed on eligible individuals presenting with symptoms indicative of TB and repeated at 14 days if initially positive. Participants will be prospectively classified into three distinct groups based on National TB Control Program (NTBCP) criteria: Group A, TB notification with sputum-based laboratory confirmation; Group B, TB notification with empiric diagnosis; and Group C, individuals not notified. Group C individuals with detectable Mtb bioaerosol will be monitored until resolution of clinical and laboratory status. Collection of bioaerosol specimens will be via two consecutive sampling modalities: (1) direct sampling following a specific respiratory manoeuvre; and (2) indirect sampling during passive respiratory activity. Bioaerosol specimens will be analyzed for viable Mtb using DMN-trehalose staining and live-cell fluorescence microscopy. Mtb genomes and mycobacterial and host lipids will be detected using droplet digital PCR and mass spectrometry analyses, respectively. The primary objective is to determine the prevalence of Mtb bioaerosols in all TB clinic attendees and in each of the groups. Secondary objectives are to investigate differences in prevalence of Mtb bioaerosol by HIV status and current isoniazid preventive therapy (IPT) use; we will also determine the impact of anti-TB chemotherapy on Mtb-containing bioaerosol production. DISCUSSION Respiratory bioaerosol has a potential role in non-invasive TB diagnosis, infectivity measurement and treatment monitoring. TRIAL REGISTRATION ClinicalTrials.gov: NCT04241809 . Date of Registration: 27/1/2020.
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Affiliation(s)
- Benjamin Patterson
- University of Amsterdam, Amsterdam Institute for Global Health and Development, Amsterdam, the Netherlands
| | - Anastasia Koch
- Institute of Infectious Disease and Molecular Medicine (IDM), Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa
| | - Sophia Gessner
- Institute of Infectious Disease and Molecular Medicine (IDM), Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa
| | - Ryan Dinkele
- Institute of Infectious Disease and Molecular Medicine (IDM), Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa
| | - Melitta Gqada
- Desmond Tutu HIV Centre, Institute of Infectious Disease and Molecular Medicine (IDM), University of Cape Town, Cape Town, South Africa
| | | | - Frank Cobelens
- University of Amsterdam, Amsterdam Institute for Global Health and Development, Amsterdam, the Netherlands
| | - Francesca Little
- Department of Statistical Sciences, University of Cape Town, Cape Town, South Africa
| | - Digby F. Warner
- Institute of Infectious Disease and Molecular Medicine (IDM), Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa
| | - Robin Wood
- Institute of Infectious Disease and Molecular Medicine (IDM), Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa
- Desmond Tutu HIV Centre, Institute of Infectious Disease and Molecular Medicine (IDM), University of Cape Town, Cape Town, South Africa
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Patterson B, Wood R. Is cough really necessary for TB transmission? Tuberculosis (Edinb) 2019; 117:31-35. [PMID: 31378265 PMCID: PMC6688829 DOI: 10.1016/j.tube.2019.05.003] [Citation(s) in RCA: 46] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2019] [Revised: 04/06/2019] [Accepted: 05/13/2019] [Indexed: 10/26/2022]
Abstract
Cough has long been implicated in the production of infectious aerosol leading to transmission of tuberculosis (TB). However, prevalence studies frequently identify radiographic evidence of TB in subclinical individuals in the absence of reported coughing. Elucidating the role of cough in transmission depends on understanding the physical process of aerosolizing and expelling mycobacterium tuberculosis (Mtb) bacilli. In the last decade, human aerosol studies have progressed with improved precision of particle detection and greater sophistication of experimental protocols. Combining principles of respiratory physiology, the site and mechanism of aerosolization of respiratory lining fluids during phases of the respiratory cycle has been investigated in detail. Additionally, recent success in the direct detection of naturally generated Mtb aerosols has allowed more detailed characterization in terms of their rate of production and size distribution. We propose that TB transmission depends on the coincidence of the site of aerosol generation with the presence of Mtb bacilli. This review will examine the evidence for site of aerosol production during cough and respiratory activities in conjunction with the characteristics of detectable Mtb aerosols and locations of tuberculosis infection. Furthermore, we propose respiratory activities that are likely to optimise aerosol sampling for investigation of transmission.
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Affiliation(s)
- Benjamin Patterson
- University of Amsterdam, Amsterdam Institute for Global Health and Development, Amsterdam, the Netherlands; Desmond Tutu HIV Centre, IDM, University of Cape Town, Cape Town, South Africa.
| | - Robin Wood
- Desmond Tutu HIV Centre, IDM, University of Cape Town, Cape Town, South Africa; Institute of Infectious Disease and Molecular Medicine (IDM), Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa
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Martinez L, Verma R, Croda J, Horsburgh CR, Walter KS, Degner N, Middelkoop K, Koch A, Hermans S, Warner DF, Wood R, Cobelens F, Andrews JR. Detection, survival and infectious potential of Mycobacterium tuberculosis in the environment: a review of the evidence and epidemiological implications. Eur Respir J 2019; 53:1802302. [PMID: 31048345 PMCID: PMC6753378 DOI: 10.1183/13993003.02302-2018] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2018] [Accepted: 04/18/2019] [Indexed: 11/05/2022]
Abstract
Much remains unknown about Mycobacterium tuberculosis transmission. Seminal experimental studies from the 1950s demonstrated that airborne expulsion of droplet nuclei from an infectious tuberculosis (TB) patient is the primary route of transmission. However, these findings did not rule out other routes of M. tuberculosis transmission. We reviewed historical scientific evidence from the late 19th/early 20th century and contemporary studies investigating the presence, persistence and infectiousness of environmental M. tuberculosis We found both experimental and epidemiological evidence supporting the presence and viability of M. tuberculosis in multiple natural and built environments for months to years, presumably following contamination by a human source. Furthermore, several studies confirm M. tuberculosis viability and virulence in the environment using guinea pig and mouse models. Most of this evidence was historical; however, several recent studies have reported consistent findings of M. tuberculosis detection and viability in the environment using modern methods. Whether M. tuberculosis in environments represents an infectious threat to humans requires further investigation; this may represent an untapped source of data with which to further understand M. tuberculosis transmission. We discuss potential opportunities for harnessing these data to generate new insights into TB transmission in congregate settings.
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Affiliation(s)
- Leonardo Martinez
- Division of Infectious Diseases and Geographic Medicine, School of Medicine, Stanford University, Stanford, CA, USA
| | - Renu Verma
- Division of Infectious Diseases and Geographic Medicine, School of Medicine, Stanford University, Stanford, CA, USA
| | - Julio Croda
- Oswaldo Cruz Foundation, Campo Grande and Salvador, Brazil
- School of Medicine, Federal University of Mato Grosso do Sul, Campo Grande, Brazil
| | - C Robert Horsburgh
- Dept of Medicine, Boston University School of Medicine, Boston, MA, USA
- Dept of Epidemiology, Biostatistics and Global Health, Boston University School of Public Health, Boston, MA, USA
| | - Katharine S Walter
- Division of Infectious Diseases and Geographic Medicine, School of Medicine, Stanford University, Stanford, CA, USA
| | - Nicholas Degner
- Division of Infectious Diseases and Geographic Medicine, School of Medicine, Stanford University, Stanford, CA, USA
| | - Keren Middelkoop
- The Desmond Tutu HIV Centre, Institute for Infectious Disease and Molecular Medicine, Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa
- Dept of Medicine, University of Cape Town, Cape Town, South Africa
| | - Anastasia Koch
- SAMRC/NHLS/UCT Molecular Mycobacteriology Research Unit, Dept of Pathology and Institute of Infectious Diseases and Molecular Medicine, Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa
| | - Sabine Hermans
- The Desmond Tutu HIV Centre, Institute for Infectious Disease and Molecular Medicine, Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa
- Dept of Global Health, Amsterdam Institute for Global Health and Development, Academic Medical Center, Amsterdam, The Netherlands
| | - Digby F Warner
- SAMRC/NHLS/UCT Molecular Mycobacteriology Research Unit, Dept of Pathology and Institute of Infectious Diseases and Molecular Medicine, Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa
- Wellcome Center for Infectious Diseases Research in Africa, Institute of Infectious Diseases and Molecular Medicine, Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa
| | - Robin Wood
- The Desmond Tutu HIV Centre, Institute for Infectious Disease and Molecular Medicine, Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa
| | - Frank Cobelens
- Dept of Global Health, Amsterdam Institute for Global Health and Development, Academic Medical Center, Amsterdam, The Netherlands
| | - Jason R Andrews
- Division of Infectious Diseases and Geographic Medicine, School of Medicine, Stanford University, Stanford, CA, USA
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Shimeles E, Enquselassie F, Aseffa A, Tilahun M, Mekonen A, Wondimagegn G, Hailu T. Risk factors for tuberculosis: A case-control study in Addis Ababa, Ethiopia. PLoS One 2019; 14:e0214235. [PMID: 30939169 PMCID: PMC6445425 DOI: 10.1371/journal.pone.0214235] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2018] [Accepted: 03/08/2019] [Indexed: 11/23/2022] Open
Abstract
Background Tuberculosis remains a major public-health problem in the world, despite several efforts to improve case identification and treatment compliance. It is well known cause of ill-health among millions of people each year and ranks as the second leading cause of death from infectious disease worldwide. Despite implementation of the World health organization recommended strategy, the reductions in the incidence of TB have been minimal in high burden countries. Objectives and methods A case control study was carried out to assess the risk factors of TB, where cases were newly registered bacteriologically confirmed pulmonary TB patients with age greater than 15 years who present at twenty health centres in Addis Ababa. Controls were age and sex matched attendees who presented in the same health centers for non-TB health problems. Results A total of 260 cases and 260 controls were enrolled in the study and 45.8% of cases and 46.2% of controls were in the 26–45 years age bracket. According to the multivariable logistic regression analysis, seven variables were found to be independent predictors for the occurrence of TB after controlling possible confounders. Patients who live in house with no window or one window were almost two times more likely to develop tuberculosis compared to people whose house has multiple windows (AOR = 1.81; 95% CI:1.06, 3.07). Previous history of hospital admission was found to pose risk almost more than three times (AOR = 3.39; 95% CI: 1.64–7.03). Having a household member who had TB was shown to increase risk of developing TB by three fold (AOR = 3.00; 95% CI: 1.60, 5.62). The study showed that illiterate TB patients were found to be more than twice more likely to develop TB compared to subjects who can atleast read and write (AOR, 95% CI = 2.15, 1.05, 4.40). Patients with household income of less than 1000 birrs per month were more than two times more likely to develop TB compared to those who had higher income (AOR = 2.2; 95% CI: 1.28, 3.78). Smoking has also been identified as important risk factor for developing TB by four times (AOR = 4.43; 95% CI: 2.10, 9.3). BCG was found to be protective against TB reducing the risk by one-third (AOR = 0.34; 95% CI: 0.22, 0.54). Conclusion This study showed that TB is more common among the most agile and economically active age group, and number of windows, history of hospital admission, a household member who had TB, illiteracy, low household income and smoking and lack of BCG scar were identified as independent risk factors. Therefore it is imperative that the TB control effort need a strategy to address socio economic issues such as poverty, overcrowding, smoking, and infection control at health care facilities level is an important intervention to prevent transmission of TB within the facilities.
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Affiliation(s)
- Ezra Shimeles
- Armauer Hanson Research Institute, ALERT Compound, Addis Ababa, Ethiopia
- School of Public health, College of Health Sciences, Addis Ababa University, Black Lion Hospital, Addis Ababa, Ethiopia
- * E-mail:
| | - Fikre Enquselassie
- School of Public health, College of Health Sciences, Addis Ababa University, Black Lion Hospital, Addis Ababa, Ethiopia
| | - Abraham Aseffa
- Armauer Hanson Research Institute, ALERT Compound, Addis Ababa, Ethiopia
| | - Melaku Tilahun
- Armauer Hanson Research Institute, ALERT Compound, Addis Ababa, Ethiopia
| | - Alemayehu Mekonen
- Ethiopian Public Health Association, Kirkos Sub City, Addis Ababa, Ethiopia
| | | | - Tsegaye Hailu
- Armauer Hanson Research Institute, ALERT Compound, Addis Ababa, Ethiopia
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12
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Peters JS, Andrews JR, Hatherill M, Hermans S, Martinez L, Schurr E, van der Heijden Y, Wood R, Rustomjee R, Kana BD. Advances in the understanding of Mycobacterium tuberculosis transmission in HIV-endemic settings. THE LANCET. INFECTIOUS DISEASES 2019; 19:e65-e76. [PMID: 30554995 PMCID: PMC6401310 DOI: 10.1016/s1473-3099(18)30477-8] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/14/2018] [Revised: 07/18/2018] [Accepted: 07/19/2018] [Indexed: 12/28/2022]
Abstract
Tuberculosis claims more human lives than any other infectious disease. This alarming epidemic has fuelled the development of novel antimicrobials and diagnostics. However, public health interventions that interrupt transmission have been slow to emerge, particularly in HIV-endemic settings. Transmission of tuberculosis is complex, involving various environmental, bacteriological, and host factors, among which concomitant HIV infection is important. Preventing person-to-person spread is central to halting the epidemic and, consequently, tuberculosis transmission is now being studied with renewed interest. In this Series paper, we review recent advances in the understanding of tuberculosis transmission, from the view of source-case infectiousness, inherent susceptibility of exposed individuals, appending tools for predicting risk of disease progression, the biophysical nature of the contagion, and the environments in which transmission occurs and is sustained in populations. We focus specifically on how HIV infection affects these features with a view to describing novel transmission blocking strategies in HIV-endemic settings.
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Affiliation(s)
- Julian S Peters
- Department of Science and Technology/National Research Foundation Centre of Excellence for Biomedical Tuberculosis Research, School of Pathology, Faculty of Health Sciences, University of the Witwatersrand and the National Health Laboratory Service, Johannesburg, South Africa
| | - Jason R Andrews
- Division of Infectious Diseases and Geographic Medicine, School of Medicine, Stanford University, Stanford, CA, USA
| | - Mark Hatherill
- South African Tuberculosis Vaccine Initiative, Institute of Infectious Disease & Molecular Medicine, University of Cape Town, Cape Town, South Africa
| | - Sabine Hermans
- Desmond Tutu HIV Centre, Institute of Infectious Disease & Molecular Medicine, University of Cape Town, Cape Town, South Africa; Department of Global Health, Amsterdam Institute for Global Health and Development, Amsterdam University Medical Center, University of Amsterdam, Amsterdam, Netherlands
| | - Leonardo Martinez
- Division of Infectious Diseases and Geographic Medicine, School of Medicine, Stanford University, Stanford, CA, USA
| | - Erwin Schurr
- Research Institute of the McGill University Health Centre, Montréal, QC, Canada
| | - Yuri van der Heijden
- Vanderbilt Tuberculosis Center and Division of Infectious Diseases, Department of Medicine, Vanderbilt University School of Medicine, Nashville, TN, USA
| | - Robin Wood
- Desmond Tutu HIV Centre, Institute of Infectious Disease & Molecular Medicine, University of Cape Town, Cape Town, South Africa
| | - Roxana Rustomjee
- Tuberculosis Clinical Research Branch, Therapeutic Research Program, Division of AIDS National Institute of Allergy and Infectious Diseases, National Institutes of Health, North Bethesda, MD, USA
| | - Bavesh D Kana
- Department of Science and Technology/National Research Foundation Centre of Excellence for Biomedical Tuberculosis Research, School of Pathology, Faculty of Health Sciences, University of the Witwatersrand and the National Health Laboratory Service, Johannesburg, South Africa; South African Medical Research Council HIV-TB Pathogenesis and Treatment Research Unit, Centre for the AIDS Programme of Research in South Africa, Durban, South Africa.
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13
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Nelson KN, Shah NS, Mathema B, Ismail N, Brust JCM, Brown TS, Auld SC, Omar SV, Morris N, Campbell A, Allana S, Moodley P, Mlisana K, Gandhi NR. Spatial Patterns of Extensively Drug-Resistant Tuberculosis Transmission in KwaZulu-Natal, South Africa. J Infect Dis 2018; 218:1964-1973. [PMID: 29961879 PMCID: PMC6217717 DOI: 10.1093/infdis/jiy394] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2018] [Accepted: 06/26/2018] [Indexed: 12/29/2022] Open
Abstract
Background Transmission is driving the global drug-resistant tuberculosis (TB) epidemic; nearly three-quarters of drug-resistant TB cases are attributable to transmission. Geographic patterns of disease incidence, combined with information on probable transmission links, can define the spatial scale of transmission and generate hypotheses about factors driving transmission patterns. Methods We combined whole-genome sequencing data with home Global Positioning System coordinates from 344 participants with extensively drug-resistant (XDR) TB in KwaZulu-Natal, South Africa, diagnosed from 2011 to 2014. We aimed to determine if genomically linked (difference of ≤5 single-nucleotide polymorphisms) cases lived close to one another, which would suggest a role for local community settings in transmission. Results One hundred eighty-two study participants were genomically linked, comprising 1084 case-pairs. The median distance between case-pairs' homes was 108 km (interquartile range, 64-162 km). Between-district, as compared to within-district, links accounted for the majority (912/1084 [84%]) of genomic links. Half (526 [49%]) of genomic links involved a case from Durban, the urban center of KwaZulu-Natal. Conclusions The high proportions of between-district links with Durban provide insight into possible drivers of province-wide XDR-TB transmission, including urban-rural migration. Further research should focus on characterizing the contribution of these drivers to overall XDR-TB transmission in KwaZulu-Natal to inform design of targeted strategies to curb the drug-resistant TB epidemic.
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Affiliation(s)
- Kristin N Nelson
- Rollins School of Public Health, Emory University, Atlanta, Georgia
| | - N Sarita Shah
- Rollins School of Public Health, Emory University, Atlanta, Georgia
- Centers for Disease Control and Prevention, Atlanta, Georgia
| | - Barun Mathema
- Mailman School of Public Health, Columbia University, New York, New York
| | - Nazir Ismail
- National Institute for Communicable Diseases, Johannesburg
- University of Pretoria, South Africa
| | - James C M Brust
- Albert Einstein College of Medicine and Montefiore Medical Center, Bronx, New York
| | - Tyler S Brown
- Infectious Diseases Division, Massachusetts General Hospital, Boston
| | - Sara C Auld
- Rollins School of Public Health, Emory University, Atlanta, Georgia
- Emory University School of Medicine, Atlanta, Georgia
| | | | - Natashia Morris
- Environment and Health Research Unit, South African Medical Research Council, Johannesburg
| | - Angie Campbell
- Rollins School of Public Health, Emory University, Atlanta, Georgia
| | - Salim Allana
- Rollins School of Public Health, Emory University, Atlanta, Georgia
| | - Pravi Moodley
- National Health Laboratory Service, University of KwaZulu-Natal, Durban, South Africa
- School of Laboratory Medicine and Medical Sciences, University of KwaZulu-Natal, Durban, South Africa
| | - Koleka Mlisana
- National Health Laboratory Service, University of KwaZulu-Natal, Durban, South Africa
- School of Laboratory Medicine and Medical Sciences, University of KwaZulu-Natal, Durban, South Africa
| | - Neel R Gandhi
- Rollins School of Public Health, Emory University, Atlanta, Georgia
- Emory University School of Medicine, Atlanta, Georgia
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14
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Abstract
Objective: The risk of transmission of Mycobacterium tuberculosis in antiretroviral therapy (ART) clinics is recognized, particularly, when HIV and tuberculosis services are unified, but the degree of potential exposure to patients with infectious tuberculosis has not been measured. We aimed to quantify this clinic exposure. Methods: Over 1 year, we recorded all visits to a clinic in northern Malawi that offers HIV testing and counselling, HIV care, ART, and TB diagnostic and treatment services. We included patients and guardians, noting timing and reason for the visit, using a palm vein reader to assist recognition of individuals and record times automatically. Screening for tuberculosis was enhanced, including induced sputum if necessary. Results: Information was collected on 5011 individuals and 19 426 visits. During the period, 90 individuals with bacteriologically confirmed pulmonary tuberculosis attended the clinic when they were likely to have been infectious (taken as 6 weeks before diagnosis to 2 weeks after the start of treatment), including 76 who attended before tuberculosis was diagnosed or suspected. We estimated that 19% of visits had at least 1 h of potential exposure to patients with infectious tuberculosis, half to patients attending prediagnosis. Conclusion: There was considerable risk of exposure, including of immunosuppressed patients, to patients with infectious tuberculosis, especially as repeated visits are made. Much of this exposure could not be avoided by separation of patients with known tuberculosis. Good ventilation and avoidance of crowding is essential to minimize transmission of M. tuberculosis in this type of setting.
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15
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Auld SC, Shah NS, Mathema B, Brown TS, Ismail N, Omar SV, Brust JCM, Nelson KN, Allana S, Campbell A, Mlisana K, Moodley P, Gandhi NR. Extensively drug-resistant tuberculosis in South Africa: genomic evidence supporting transmission in communities. Eur Respir J 2018; 52:13993003.00246-2018. [PMID: 30115614 DOI: 10.1183/13993003.00246-2018] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2018] [Accepted: 08/08/2018] [Indexed: 11/05/2022]
Abstract
Despite evidence that transmission is driving an extensively drug-resistant TB (XDR-TB) epidemic, our understanding of where and between whom transmission occurs is limited. We sought to determine whether there was genomic evidence of transmission between individuals without an epidemiologic connection.We conducted a prospective study of XDR-TB patients in KwaZulu-Natal, South Africa, during the 2011-2014 period. We collected sociodemographic and clinical data, and identified epidemiologic links based on person-to-person or hospital-based connections. We performed whole-genome sequencing (WGS) on the Mycobacterium tuberculosis isolates and determined pairwise single nucleotide polymorphism (SNP) differences.Among 404 participants, 123 (30%) had person-to-person or hospital-based links, leaving 281 (70%) epidemiologically unlinked. The median SNP difference between participants with person-to-person and hospital-based links was 10 (interquartile range (IQR) 8-24) and 16 (IQR 10-23), respectively. The median SNP difference between unlinked participants and their closest genomic link was 5 (IQR 3-9) and half of unlinked participants were within 7 SNPs of at least five participants.The majority of epidemiologically-unlinked XDR-TB patients had low pairwise SNP differences with at least one other participant, consistent with transmission. These data suggest that much of transmission may result from casual contact in community settings between individuals not known to one another.
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Affiliation(s)
- Sara C Auld
- School of Medicine, Emory University, Atlanta, GA, USA.,Rollins School of Public Health, Emory University, Atlanta, GA, USA
| | - N Sarita Shah
- Rollins School of Public Health, Emory University, Atlanta, GA, USA.,Centers for Disease Control and Prevention, Atlanta, GA, USA
| | - Barun Mathema
- Mailman School of Public Health, Columbia University, New York, NY, USA
| | - Tyler S Brown
- Mailman School of Public Health, Columbia University, New York, NY, USA.,Massachusetts General Hospital, Boston, MA, USA
| | - Nazir Ismail
- National Institute for Communicable Diseases, Johannesburg, South Africa.,Dept of Medical Microbiology, University of Pretoria, Pretoria, South Africa
| | - Shaheed Vally Omar
- National Institute for Communicable Diseases, Johannesburg, South Africa
| | | | - Kristin N Nelson
- Rollins School of Public Health, Emory University, Atlanta, GA, USA
| | - Salim Allana
- Rollins School of Public Health, Emory University, Atlanta, GA, USA
| | - Angela Campbell
- Rollins School of Public Health, Emory University, Atlanta, GA, USA
| | - Koleka Mlisana
- School of Laboratory Medicine and Medical Sciences, University of KwaZulu-Natal, Durban, South Africa.,National Health Laboratory Service, Durban, South Africa
| | - Pravi Moodley
- National Health Laboratory Service, Durban, South Africa
| | - Neel R Gandhi
- School of Medicine, Emory University, Atlanta, GA, USA.,Rollins School of Public Health, Emory University, Atlanta, GA, USA
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16
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Mathema B, Andrews JR, Cohen T, Borgdorff MW, Behr M, Glynn JR, Rustomjee R, Silk BJ, Wood R. Drivers of Tuberculosis Transmission. J Infect Dis 2017; 216:S644-S653. [PMID: 29112745 PMCID: PMC5853844 DOI: 10.1093/infdis/jix354] [Citation(s) in RCA: 87] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Measuring tuberculosis transmission is exceedingly difficult, given the remarkable variability in the timing of clinical disease after Mycobacterium tuberculosis infection; incident disease can result from either a recent (ie, weeks to months) or a remote (ie, several years to decades) infection event. Although we cannot identify with certainty the timing and location of tuberculosis transmission for individuals, approaches for estimating the individual probability of recent transmission and for estimating the fraction of tuberculosis cases due to recent transmission in populations have been developed. Data used to estimate the probable burden of recent transmission include tuberculosis case notifications in young children and trends in tuberculin skin test and interferon γ-release assays. More recently, M. tuberculosis whole-genome sequencing has been used to estimate population levels of recent transmission, identify the distribution of specific strains within communities, and decipher chains of transmission among culture-positive tuberculosis cases. The factors that drive the transmission of tuberculosis in communities depend on the burden of prevalent tuberculosis; the ways in which individuals live, work, and interact (eg, congregate settings); and the capacity of healthcare and public health systems to identify and effectively treat individuals with infectious forms of tuberculosis. Here we provide an overview of these factors, describe tools for measurement of ongoing transmission, and highlight knowledge gaps that must be addressed.
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Affiliation(s)
- Barun Mathema
- Department of Epidemiology, Mailman School of Public Health, Columbia University, New York, New York
| | - Jason R Andrews
- Division of Infectious Diseases and Geographic Medicine, Stanford University, California
| | - Ted Cohen
- Department of Epidemiology of Microbial Diseases, Yale School of Public Health, New Haven, Connecticut
| | - Martien W Borgdorff
- Centers for Disease Control and Prevention, Kisumu, Kenya
- Department of Clinical Epidemiology, Biostatistics, and Bioinformatics, Academic Medical Center, University of Amsterdam, the Netherlands
| | - Marcel Behr
- McGill International TB Centre, Research Institute of the McGill University Health Centre, Montreal,Canada
| | - Judith R Glynn
- Faculty of Epidemiology and Population Health, London School of Hygiene and Tropical Medicine, United Kingdom
| | - Roxana Rustomjee
- Tuberculosis Clinical Research Branch, Therapeutics Research Program, Division of AIDS, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Department of Health and Human Services, Rockville, Maryland
| | - Benjamin J Silk
- Division of Tuberculosis Elimination, Centers for Disease Control and Prevention, Atlanta, Georgia
| | - Robin Wood
- Desmond Tutu HIV Centre, Institute of Infectious Disease and Molecular Medicine, University of Cape Town, South Africa
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17
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Martinez L, Shen Y, Mupere E, Kizza A, Hill PC, Whalen CC. Transmission of Mycobacterium Tuberculosis in Households and the Community: A Systematic Review and Meta-Analysis. Am J Epidemiol 2017; 185:1327-1339. [PMID: 28982226 PMCID: PMC6248487 DOI: 10.1093/aje/kwx025] [Citation(s) in RCA: 90] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2015] [Revised: 06/02/2016] [Accepted: 06/02/2016] [Indexed: 12/19/2022] Open
Abstract
The individual- and population-level impact of household tuberculosis exposure on transmission is unclear but may have implications for the effectiveness and implementation of control interventions. We systematically searched for and included studies in which latent tuberculosis infection was assessed in 2 groups: children exposed and unexposed to a household member with tuberculosis. We also extracted data on the smear and culture status of index cases, the age and bacillus Calmette-Guérin vaccination status of contacts, and study design characteristics. Of 6,176 citations identified from our search strategy, 26 studies (13,999 children with household exposure to tuberculosis and 174,097 children without) from 1929-2015 met inclusion criteria. Exposed children were 3.79 (95% confidence interval (CI): 3.01, 4.78) times more likely to be infected than were their community counterparts. Metaregression demonstrated higher infection among children aged 0-4 years of age compared with children aged 10-14 years (ratio of odds ratios = 2.24, 95% CI: 1.43, 3.51) and among smear-positive versus smear-negative index cases (ratio of odds ratios = 5.45, 95% CI: 3.43, 8.64). At the population level, we estimated that a small proportion (<20%) of transmission was attributable to household exposure. Our results suggest that targeting tuberculosis prevention efforts to household contacts is highly effective. However, a large proportion of transmission at the population level may occur outside the household.
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Affiliation(s)
- Leonardo Martinez
- Department of Epidemiology and Biostatistics, College of Public Health,
University of Georgia, Athens, Georgia
- Institute of Global Health, College of Public Health, University of
Georgia, Athens, Georgia
| | - Ye Shen
- Department of Epidemiology and Biostatistics, College of Public Health,
University of Georgia, Athens, Georgia
| | - Ezekiel Mupere
- Department of Paediatrics and Child Health, College of Health Sciences,
Makerere University, Kampala, Uganda
- Uganda–Case Western Reserve University Research Collaboration,
Tuberculosis Research Unit, Kampala, Uganda
| | - Allan Kizza
- Department of Epidemiology and Biostatistics, College of Public Health,
University of Georgia, Athens, Georgia
| | - Philip C. Hill
- Department of Preventive and Social Medicine, Centre for International
Health and the Otago International Health Research Network, University of Otago Medical
School, Dunedin, New Zealand
| | - Christopher C. Whalen
- Department of Epidemiology and Biostatistics, College of Public Health,
University of Georgia, Athens, Georgia
- Institute of Global Health, College of Public Health, University of
Georgia, Athens, Georgia
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18
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Yates TA, Tanser F, Abubakar I. Plan Beta for tuberculosis: it's time to think seriously about poorly ventilated congregate settings. Int J Tuberc Lung Dis 2016; 20:5-10. [PMID: 26688524 PMCID: PMC4677622 DOI: 10.5588/ijtld.15.0494] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Globally, the rates of decline in tuberculosis (TB) incidence are disappointing, but in line with model predictions regarding the likely impact of the DOTS strategy. Here, we review evidence from basic epidemiology, molecular epidemiology and modelling, all of which suggest that, in high-burden settings, the majority of Mycobacterium tuberculosis transmission may occur in indoor congregate settings. We argue that mass environmental modifications in these places might have a significant impact on TB control and suggest a research agenda that might inform interventions of this nature. The necessary technology exists and, critically, implementation would not be dependent on health care workers who are in short supply in the communities worst affected by TB.
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Affiliation(s)
- T A Yates
- Centre for Infectious Disease Epidemiology, Research Department of Infection and Population Health, University College London, London, UK; Wellcome Trust Africa Centre for Population Health, University of KwaZulu-Natal, Mtubatuba, South Africa
| | - F Tanser
- Wellcome Trust Africa Centre for Population Health, University of KwaZulu-Natal, Mtubatuba, South Africa; School of Nursing and Public Health, University of KwaZulu-Natal, Durban, South Africa
| | - I Abubakar
- Centre for Infectious Disease Epidemiology, Research Department of Infection and Population Health, University College London, London, UK; Medical Research Council Clinical Trials Unit, University College London, London, UK
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19
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Khan PY, Glynn JR, Fielding KL, Mzembe T, Mulawa D, Chiumya R, Fine PEM, Koole O, Kranzer K, Crampin AC. Risk factors for Mycobacterium tuberculosis infection in 2-4 year olds in a rural HIV-prevalent setting. Int J Tuberc Lung Dis 2016; 20:342-9. [PMID: 27046715 PMCID: PMC4743681 DOI: 10.5588/ijtld.15.0672] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2015] [Accepted: 10/05/2015] [Indexed: 11/24/2022] Open
Abstract
BACKGROUND Mycobacterium tuberculosis infection in children acts as a sentinel for infectious tuberculosis. OBJECTIVE To assess risk factors associated with tuberculous infection in pre-school children. METHOD We conducted a population-wide tuberculin skin test (TST) survey from January to December 2012 in Malawi. All children aged 2-4 years residing in a demographic surveillance area were eligible. Detailed demographic data, including adult human immunodeficiency virus (HIV) status, and clinical and sociodemographic data on all diagnosed tuberculosis (TB) patients were available. RESULTS The prevalence of M. tuberculosis infection was 1.1% using a TST induration cut-off of 15 mm (estimated annual risk of infection of 0.3%). The main identifiable risk factors were maternal HIV infection at birth (adjusted OR [aOR] 3.6, 95%CI 1.1-12.2), having three or more adult members in the household over a lifetime (aOR 2.4, 95%CI 1.2-4.8) and living in close proximity to a known case of infectious TB (aOR 1.6, 95%CI 1.1-2.4), modelled as a linear variable across categories (>200 m, 100-200 m, <100 m, within household). Less than 20% of the infected children lived within 200 m of a known diagnosed case. CONCLUSION Household and community risk factors identified do not explain the majority of M. tuberculosis infections in children in our setting.
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Affiliation(s)
- P Y Khan
- Department of Infectious Disease Epidemiology, London School of Hygiene & Tropical Medicine, Keppel Street, London WD1E 7HT, UK; Karonga Prevention Study, Chilumba, Malawi.
| | - J R Glynn
- Department of Infectious Disease Epidemiology, London School of Hygiene & Tropical Medicine, London, UK
| | - K L Fielding
- Department of Infectious Disease Epidemiology, London School of Hygiene & Tropical Medicine, London, UK
| | - T Mzembe
- Karonga Prevention Study, Chilumba, Malawi
| | - D Mulawa
- Karonga Prevention Study, Chilumba, Malawi
| | - R Chiumya
- Karonga Prevention Study, Chilumba, Malawi
| | - P E M Fine
- Department of Infectious Disease Epidemiology, London School of Hygiene & Tropical Medicine, London, UK
| | - O Koole
- Department of Infectious Disease Epidemiology, London School of Hygiene & Tropical Medicine, London, UK; Karonga Prevention Study, Chilumba, Malawi
| | - K Kranzer
- National and Supranational Mycobacterium Reference Laboratory, Forschungszentrum Borstel, Borstel, Germany
| | - A C Crampin
- Department of Infectious Disease Epidemiology, London School of Hygiene & Tropical Medicine, London, UK; Karonga Prevention Study, Chilumba, Malawi
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20
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Dodd PJ, Looker C, Plumb ID, Bond V, Schaap A, Shanaube K, Muyoyeta M, Vynnycky E, Godfrey-Faussett P, Corbett EL, Beyers N, Ayles H, White RG. Age- and Sex-Specific Social Contact Patterns and Incidence of Mycobacterium tuberculosis Infection. Am J Epidemiol 2016; 183:156-66. [PMID: 26646292 PMCID: PMC4706676 DOI: 10.1093/aje/kwv160] [Citation(s) in RCA: 87] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2014] [Accepted: 06/15/2015] [Indexed: 11/13/2022] Open
Abstract
We aimed to model the incidence of infection with Mycobacterium tuberculosis among adults using data on infection incidence in children, disease prevalence in adults, and social contact patterns. We conducted a cross-sectional face-to-face survey of adults in 2011, enumerating "close" (shared conversation) and "casual" (shared indoor space) social contacts in 16 Zambian communities and 8 South African communities. We modeled the incidence of M. tuberculosis infection in all age groups using these contact patterns, as well as the observed incidence of M. tuberculosis infection in children and the prevalence of tuberculosis disease in adults. A total of 3,528 adults participated in the study. The reported rates of close and casual contact were 4.9 per adult per day (95% confidence interval: 4.6, 5.2) and 10.4 per adult per day (95% confidence interval: 9.3, 11.6), respectively. Rates of close contact were higher for adults in larger households and rural areas. There was preferential mixing of close contacts within age groups and within sexes. The estimated incidence of M. tuberculosis infection in adults was 1.5-6 times higher (2.5%-10% per year) than that in children. More than 50% of infections in men, women, and children were estimated to be due to contact with adult men. We conclude that estimates of infection incidence based on surveys in children might underestimate incidence in adults. Most infections may be due to contact with adult men. Treatment and control of tuberculosis in men is critical to protecting men, women, and children from tuberculosis.
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Affiliation(s)
| | | | | | | | | | | | | | | | | | | | | | | | - Richard G. White
- Correspondence to Dr. Richard G. White, TB Modelling Group, Department of Infectious Disease Epidemiology, London School of Hygiene & Tropical Medicine, Keppel Street, London WC1E 7HT (e-mail: )
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21
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Brief Report: The Effect of Antiretroviral Therapy and CD4 Count on Markers of Infectiousness in HIV-Associated Tuberculosis. J Acquir Immune Defic Syndr 2015; 70:104-8. [PMID: 26322671 DOI: 10.1097/qai.0000000000000684] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Clinical features of tuberculosis influence infectiousness. This cross-sectional study examined the effect of combination antiretroviral therapy (cART) and CD4 on sputum smear-positivity (SS+) and pulmonary cavitation among 1589 (1185/1589 HIV-positive) miners in South Africa. Proportions SS+ varied nonlinearly by CD4 with greatest proportions SS+ (55.3%) in the lowest stratum (<100 cells/μL). Adjusted prevalence ratio for SS+; on vs. off cART was 0.90 (95% confidence interval: 0.73 to 1.11). Proportions with cavitation varied linearly with CD4, with no independent cART effect (adjusted prevalence ratio 1.17; 95% confidence interval: 0.80 to 1.71). cART did not independently affect SS+ or cavitation but may increase infectiousness through CD4 recovery.
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Glynn JR, Guerra-Assunção JA, Houben RMGJ, Sichali L, Mzembe T, Mwaungulu LK, Mwaungulu JN, McNerney R, Khan P, Parkhill J, Crampin AC, Clark TG. Whole Genome Sequencing Shows a Low Proportion of Tuberculosis Disease Is Attributable to Known Close Contacts in Rural Malawi. PLoS One 2015; 10:e0132840. [PMID: 26181760 PMCID: PMC4504505 DOI: 10.1371/journal.pone.0132840] [Citation(s) in RCA: 74] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2015] [Accepted: 06/18/2015] [Indexed: 12/12/2022] Open
Abstract
Background The proportion of tuberculosis attributable to transmission from close contacts is not well known. Comparison of the genome of strains from index patients and prior contacts allows transmission to be confirmed or excluded. Methods In Karonga District, Malawi, all tuberculosis patients are asked about prior contact with others with tuberculosis. All available strains from culture-positive patients were sequenced. Up to 10 single nucleotide polymorphisms between index patients and their prior contacts were allowed for confirmation, and ≥ 100 for exclusion. The population attributable fraction was estimated from the proportion of confirmed transmissions and the proportion of patients with contacts. Results From 1997–2010 there were 1907 new culture-confirmed tuberculosis patients, of whom 32% reported at least one family contact and an additional 11% had at least one other contact; 60% of contacts had smear-positive disease. Among case-contact pairs with sequences available, transmission was confirmed from 38% (62/163) smear-positive prior contacts and 0/17 smear-negative prior contacts. Confirmed transmission was more common in those related to the prior contact (42.4%, 56/132) than in non-relatives (19.4%, 6/31, p = 0.02), and in those with more intense contact, to younger index cases, and in more recent years. The proportion of tuberculosis attributable to known contacts was estimated to be 9.4% overall. Conclusions In this population known contacts only explained a small proportion of tuberculosis cases. Even those with a prior family contact with smear positive tuberculosis were more likely to have acquired their infection elsewhere.
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Affiliation(s)
- Judith R. Glynn
- Faculty of Epidemiology and Population Health, London School of Hygiene & Tropical Medicine, London, United Kingdom
- * E-mail:
| | - José Afonso Guerra-Assunção
- Faculty of Epidemiology and Population Health, London School of Hygiene & Tropical Medicine, London, United Kingdom
| | - Rein M. G. J. Houben
- Faculty of Epidemiology and Population Health, London School of Hygiene & Tropical Medicine, London, United Kingdom
| | | | | | | | | | - Ruth McNerney
- Faculty of Infectious and Tropical Diseases, London School of Hygiene & Tropical Medicine, London, United Kingdom
| | - Palwasha Khan
- Faculty of Epidemiology and Population Health, London School of Hygiene & Tropical Medicine, London, United Kingdom
| | | | - Amelia C. Crampin
- Faculty of Epidemiology and Population Health, London School of Hygiene & Tropical Medicine, London, United Kingdom
- Karonga Prevention Study, Chilumba, Malawi
| | - Taane G. Clark
- Faculty of Epidemiology and Population Health, London School of Hygiene & Tropical Medicine, London, United Kingdom
- Faculty of Infectious and Tropical Diseases, London School of Hygiene & Tropical Medicine, London, United Kingdom
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Chamie G, Wandera B, Marquez C, Kato-Maeda M, Kamya MR, Havlir DV, Charlebois ED. Identifying locations of recent TB transmission in rural Uganda: a multidisciplinary approach. Trop Med Int Health 2015; 20:537-45. [PMID: 25583212 DOI: 10.1111/tmi.12459] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
OBJECTIVES Targeting high Tuberculosis (TB) transmission sites may offer a novel approach to TB prevention in sub-Saharan Africa. We sought to characterise TB transmission sites in a rural Ugandan township. METHODS We recruited adults starting TB treatment in Tororo, Uganda, over 1 year. Fifty four TB cases provided names of frequent contacts, sites of residence, health care, work and social activities, and two sputum samples. Mycobacterium tuberculosis (MTB) culture-positive specimens underwent spoligotyping to identify strains with shared genotypes. We visualised TB case social networks, and obtained, mapped and geo-coded global positioning system measures for every location that cases reported frequenting 1 month before treatment. Locations of spatial overlap among genotype-clustered cases were considered potential transmission sites. RESULTS Six distinct genotypic clusters were identified involving 21 of 33 (64%) MTB culture-positive, genotyped cases; none shared a home. Although 18 of 54 (33%) TB cases shared social network ties, none of the genotype-clustered cases shared social ties. Using spatial analysis, we identified potential sites of within-cluster TB transmission for five of six genotypic clusters. All sites but one were healthcare and social venues, including sites of drinking, worship and marketplaces. Cases reported spending the largest proportion of pre-treatment person-time (22.4%) at drinking venues. CONCLUSIONS Using molecular epidemiology, geospatial and social network data from adult TB cases identified at clinics, we quantified person-time spent at high-risk locations across a rural Ugandan community and determined the most likely sites of recent TB transmission to be healthcare and social venues. These sites may not have been identified using contact investigation alone.
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Affiliation(s)
- Gabriel Chamie
- HIV/AIDS Division, Department of Medicine, San Francisco General Hospital, University of California, San Francisco, CA, USA; Makerere University-University of California, San Francisco (MU-UCSF) Research Collaboration, Kampala, Uganda
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Kirenga BJ, Ssengooba W, Muwonge C, Nakiyingi L, Kyaligonza S, Kasozi S, Mugabe F, Boeree M, Joloba M, Okwera A. Tuberculosis risk factors among tuberculosis patients in Kampala, Uganda: implications for tuberculosis control. BMC Public Health 2015; 15:13. [PMID: 25604986 PMCID: PMC4311451 DOI: 10.1186/s12889-015-1376-3] [Citation(s) in RCA: 49] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2014] [Accepted: 01/08/2015] [Indexed: 11/10/2022] Open
Abstract
Background Slow decline in the incidence of tuberculosis (TB) has been observed in most high TB burden countries. Knowledge of the prevalence of different TB risk factors can help expand TB control strategies. However with the exception of Human Immunodeficiency Virus (HIV) the prevalence of the other TB risk factors are poorly studied in Uganda. We aimed to determine the prevalence of different TB risk factors and TB disease presentation among TB patients in Kampala Uganda. Methods We assessed 365 adult TB patients and used descriptive statistics to summarize their socio-demographic, clinical, radiological, sputum mycobacteriology and TB risk factors (HIV, diabetes, TB contact, alcohol use, tobacco smoking, poverty and overcrowding) data. Results A total of 158 (43.3%) patients were male and the median age was 29 (IQR 28–30). Majority of the patients (89.2%) had pulmonary TB, 86.9% were new and 13.2% were retreatment. Wasting (i.e. body mass index of <18.5 kg/m2) was found in 38.5% of the patients and 63% presented with cough. Constitutional symptoms (fever, anorexia, night sweats and weight loss) were reported by 32.1%. Most patients (78.6%) presented with non-cavity lung parenchyma disease (infiltrates, nodules, masses) but 35.2% had cavity disease. Pleural disease was detected in 19.3% of patients. Positive smear microscopy and culture (irrespective of month of treatment) was found in 52.7% and 36.5% of patients respectively. Any drug resistance was detected in 21.1% of patients while multidrug resistance (MDR) TB defined as resistance to rifampicin and isoniazid was detected in 6.3% of patients. All MDR patients were new patients. The prevalence of TB risk factors were as follows: HIV 41.4%, diabetes 5.4%, close contact 11.5%, family history 17.5%, smoking 26.37%, poverty 39.5%, overcrowding 57.3% and alcohol use 50.7%. Overcrowding increased smear positive rate, prevalence ratio 1.22, p = 0.09 but all the other studied risk factors did not affect clinical, radiological and mycobacteriological study patient characteristics. Conclusions Among TB patients in Kampala, Uganda, there is high prevalence of the known TB risk factors. Targeting reducing their prevalence may lead to better TB control in the country. Tuberculosis, risk factors, Uganda.
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Affiliation(s)
- Bruce J Kirenga
- Department of Medicine, Makerere University College of Health Sciences, P.O. Box 7072, Kampala, Uganda.
| | - Willy Ssengooba
- Department of Microbiology, Makerere University College of Health Sciences, Kampala, Uganda. .,Department of Global Health and Amsterdam Institute of Global Health and Development, Academic Medical Center, University of Amsterdam, P.O. Box 22700, 1100, DE, Amsterdam, Netherlands.
| | - Catherine Muwonge
- National Tuberculosis and Leprosy Program, Ministry of Health, Kampala, Uganda.
| | - Lydia Nakiyingi
- Department of Medicine, Makerere University College of Health Sciences, P.O. Box 7072, Kampala, Uganda.
| | - Stephen Kyaligonza
- National Tuberculosis and Leprosy Program, Ministry of Health, Kampala, Uganda.
| | - Samuel Kasozi
- National Tuberculosis and Leprosy Program, Ministry of Health, Kampala, Uganda.
| | - Frank Mugabe
- National Tuberculosis and Leprosy Program, Ministry of Health, Kampala, Uganda.
| | - Martin Boeree
- Department of Pulmonary Diseases, Radboud University Nijmegen Medical Center, Nijmegen, The Netherlands.
| | - Moses Joloba
- Department of Microbiology, Makerere University College of Health Sciences, Kampala, Uganda.
| | - Alphonse Okwera
- National Tuberculosis treatment unit, Mulago Hospital, Kampala, Uganda.
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Wang W, Mathema B, Hu Y, Zhao Q, Jiang W, Xu B. Role of casual contacts in the recent transmission of tuberculosis in settings with high disease burden. Clin Microbiol Infect 2014; 20:1140-5. [PMID: 24941878 DOI: 10.1111/1469-0691.12726] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2014] [Revised: 06/14/2014] [Accepted: 06/14/2014] [Indexed: 01/18/2023]
Abstract
Tuberculosis (TB) remains a major cause of morbidity and mortality worldwide. It is expected that combining multiple molecular methods will further help in focusing contact investigations. We performed a population-based molecular epidemiological study in six sites in China between 1 June 2009 and 31 December 2010. A genotyping method combining 7-loci MIRU-VNTR and IS6110-based RFLP was employed to determine predictors of recent transmission. A second interview was performed with the clustered patients to identify potential epidemiological links. The molecular clustering analysis revealed that 187 isolates (15.3%) were clustered by sharing identical VNTR-IS6110 combined patterns, with an estimated recent transmission index being 8.9%. None of these patients reported having contacts with other members within the same cluster. Nineteen of 121 reported having a history of contact with a TB case within 2 years before the current TB diagnosis. Additionally, geographical correlation was established for 19 cases in nine clusters, while only one possible epidemiological link was established in secondary interview. The results underscore the role of casual contact or reactivation of latent TB as a driving factor maintaining the current endemicity in rural China, with high disease burdens of tuberculosis.
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Affiliation(s)
- W Wang
- Department of Epidemiology, School of Public Health, Fudan University, Shanghai, China; Key Laboratory of Public Health Safety (Ministry of Education), Shanghai, China
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Roche B, Broutin H, Choisy M, Godreuil S, de Magny GC, Chevaleyre Y, Zucker JD, Breban R, Cazelles B, Simard F. The niche reduction approach: an opportunity for optimal control of infectious diseases in low-income countries? BMC Public Health 2014; 14:753. [PMID: 25062818 PMCID: PMC4124157 DOI: 10.1186/1471-2458-14-753] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2014] [Accepted: 07/17/2014] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND During the last century, WHO led public health interventions that resulted in spectacular achievements such as the worldwide eradication of smallpox and the elimination of malaria from the Western world. However, besides major successes achieved worldwide in infectious diseases control, most elimination/control programs remain frustrating in many tropical countries where specific biological and socio-economical features prevented implementation of disease control over broad spatial and temporal scales. Emblematic examples include malaria, yellow fever, measles and HIV. There is consequently an urgent need to develop affordable and sustainable disease control strategies that can target the core of infectious diseases transmission in highly endemic areas. DISCUSSION Meanwhile, although most pathogens appear so difficult to eradicate, it is surprising to realize that human activities are major drivers of the current high rate of extinction among upper organisms through alteration of their ecology and evolution, i.e., their "niche". During the last decades, the accumulation of ecological and evolutionary studies focused on infectious diseases has shown that the niche of a pathogen holds more dimensions than just the immune system targeted by vaccination and treatment. Indeed, it is situated at various intra- and inter- host levels involved on very different spatial and temporal scales. After developing a precise definition of the niche of a pathogen, we detail how major advances in the field of ecology and evolutionary biology of infectious diseases can enlighten the planning and implementation of infectious diseases control in tropical countries with challenging economic constraints. SUMMARY We develop how the approach could translate into applied cases, explore its expected benefits and constraints, and we conclude on the necessity of such approach for pathogen control in low-income countries.
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Affiliation(s)
- Benjamin Roche
- />UMMISCO (UMI 209 IRD-UPMC), Centre IRD-France Nord, 32, avenue Henry Varagnat, 93143 Bondy, Cedex, France
| | - Hélène Broutin
- />UMR MIVEGEC (IRD 224-CNRS 5290-UM1-UM2), Montpellier, France
| | - Marc Choisy
- />UMR MIVEGEC (IRD 224-CNRS 5290-UM1-UM2), Montpellier, France
- />Oxford University Clinical Research Unit, Hanoi, Vietnam
| | - Sylvain Godreuil
- />INSERM U1058 & Department of Bacteriology-Virology CHU Arnaud de Villeneuve, Montpellier, France
| | | | | | - Jean-Daniel Zucker
- />UMMISCO (UMI 209 IRD-UPMC), Centre IRD-France Nord, 32, avenue Henry Varagnat, 93143 Bondy, Cedex, France
| | | | - Bernard Cazelles
- />UMMISCO (UMI 209 IRD-UPMC), Centre IRD-France Nord, 32, avenue Henry Varagnat, 93143 Bondy, Cedex, France
- />UMR 7625 UPMC-CNRS-ENS, Paris, France
| | - Frédéric Simard
- />UMR MIVEGEC (IRD 224-CNRS 5290-UM1-UM2), Montpellier, France
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Oren E, Narita M, Nolan C, Mayer J. Neighborhood socioeconomic position and tuberculosis transmission: a retrospective cohort study. BMC Infect Dis 2014; 14:227. [PMID: 24767197 PMCID: PMC4013806 DOI: 10.1186/1471-2334-14-227] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2013] [Accepted: 04/16/2014] [Indexed: 11/29/2022] Open
Abstract
Background Current understanding of tuberculosis (TB) genotype clustering in the US is based on individual risk factors. This study sought to identify whether area-based socioeconomic status (SES) was associated with genotypic clustering among culture-confirmed TB cases. Methods A retrospective cohort analysis was performed on data collected on persons with incident TB in King County, Washington, 2004–2008. Multilevel models were used to identify the relationship between area-level SES at the block group level and clustering utilizing a socioeconomic position index (SEP). Results Of 519 patients with a known genotyping result and block group, 212 (41%) of isolates clustered genotypically. Analyses suggested an association between lower area-based SES and increased recent TB transmission, particularly among US-born populations. Models in which community characteristics were measured at the block group level demonstrated that lower area-based SEP was positively associated with genotypic clustering after controlling for individual covariates. However, the trend in higher clustering odds with lower SEP index quartile diminished when additional block-group covariates. Conclusions Results stress the need for TB control interventions that take area-based measures into account, with particular focus on poor neighborhoods. Interventions based on area-based characteristics, such as improving case finding strategies, utilizing location-based screening and addressing social inequalities, could reduce recent rates of transmission.
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Affiliation(s)
- Eyal Oren
- Division of Epidemiology & Biostatistics, University of Arizona, Tucson, AZ, USA.
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Huang CC, Tchetgen ET, Becerra MC, Cohen T, Hughes KC, Zhang Z, Calderon R, Yataco R, Contreras C, Galea J, Lecca L, Murray M. The effect of HIV-related immunosuppression on the risk of tuberculosis transmission to household contacts. Clin Infect Dis 2013; 58:765-74. [PMID: 24368620 DOI: 10.1093/cid/cit948] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
BACKGROUND Coinfection with human immunodeficiency virus (HIV) may modify the risk of transmitting tuberculosis. Some previous investigations suggest that patients coinfected with HIV and tuberculosis are less likely to transmit infection, whereas others do not support this conclusion. Here, we estimated the relative risk of tuberculosis transmission from coinfected patients compared to HIV-negative patients with tuberculosis. METHODS Between September 2009 and August 2012, we identified and enrolled 4841 household contacts of 1608 patients with drug-sensitive tuberculosis in Lima, Peru. We assessed the HIV status and CD4 counts of index patients, as well as other risk factors for infection specific to the index patient, the household, and the exposed individuals. Contacts underwent tuberculin skin testing to determine tuberculosis infection status. RESULTS After adjusting for covariates, we found that household contacts of HIV-infected tuberculosis patients with a CD4 count ≤250 cells/µL were less likely to be infected with tuberculosis (risk ratio = 0.49 [95% confidence interval, .24-.96]) than the contacts of HIV-negative tuberculosis patients. No children younger than 15 years who were exposed to HIV-positive patients with a CD4 count ≤250 cells/µL were infected with tuberculosis, compared to 22% of those exposed to non-HIV-infected patients. There was no significant difference in the risk of infection between contacts of HIV-infected index patients with CD4 counts >250 cells/µL and contacts of index patients who were not HIV-infected. CONCLUSIONS We found a reduced risk of tuberculosis infection among the household contacts of patients with active tuberculosis who had advanced HIV-related immunosuppression, suggesting reduced transmission from these index patients.
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Identification of immunological biomarkers which may differentiate latent tuberculosis from exposure to environmental nontuberculous mycobacteria in children. CLINICAL AND VACCINE IMMUNOLOGY : CVI 2013; 21:133-42. [PMID: 24285818 DOI: 10.1128/cvi.00620-13] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
A positive gamma interferon (IFN-γ) response to Mycobacterium tuberculosis early secretory antigenic target-6 (ESAT-6)/culture filtrate protein-10 (CFP-10) has been taken to indicate latent tuberculosis (TB) infection, but it may also be due to exposure to environmental nontuberculous mycobacteria in which ESAT-6 homologues are present. We assessed the immune responses to M. tuberculosis ESAT-6 and cross-reactive responses to ESAT-6 homologues of Mycobacterium avium and Mycobacterium kansasii. Archived culture supernatant samples from children at 3 years post-BCG vaccination were tested for cytokine/chemokine responses to M. tuberculosis antigens. Furthermore, the IFN-γ responses to M. tuberculosis antigens were followed up for 40 children at 8 years post-BCG vaccination, and 15 TB patients were recruited as a control group for the M. tuberculosis ESAT-6 response in Malawi. IFN-γ enzyme-linked immunosorbent assays (ELISAs) on supernatants from diluted whole-blood assays, IFN-γ enzyme-linked immunosorbent spot (ELISpot) assays, QuantiFERON TB Gold-In Tube tests, and multiplex bead assays were performed. More than 45% of the responders to M. tuberculosis ESAT-6 showed IFN-γ responses to M. avium and M. kansasii ESAT-6. In response to M. tuberculosis ESAT-6/CFP-10, interleukin 5 (IL-5), IL-9, IL-13, and IL-17 differentiated the stronger IFN-γ responders to M. tuberculosis ESAT-6 from those who preferentially responded to M. kansasii and M. avium ESAT-6. A cytokine/chemokine signature of IL-5, IL-9, IL-13, and IL-17 was identified as a putative immunological biosignature to differentiate latent TB infection from exposure to M. avium and M. kansasii in Malawian children, indicating that this signature might be particularly informative in areas where both TB and exposure to environmental nontuberculous mycobacteria are endemic.
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Fox GJ, Nhung NV, Sy DN, Britton WJ, Marks GB. Household contact investigation for tuberculosis in Vietnam: study protocol for a cluster randomized controlled trial. Trials 2013; 14:342. [PMID: 24138766 PMCID: PMC4015151 DOI: 10.1186/1745-6215-14-342] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2013] [Accepted: 10/11/2013] [Indexed: 01/28/2023] Open
Abstract
Background Tuberculosis is an infectious disease that continues to cause considerable morbidity and mortality globally. Only 65% of patients worldwide are currently diagnosed. Contact investigation is a strategy that aims to increase case detection and reduce transmission of tuberculosis, yet there is little evidence to show its effectiveness. Methods/Design We will conduct a cluster randomized controlled trial of contact investigation within the national tuberculosis control program of Vietnam. Household contacts of patients with smear-positive pulmonary tuberculosis will be invited to attend district tuberculosis units for symptom screening, examination, and chest radiography on four occasions over a two-year period. The primary endpoint is clinically confirmed tuberculosis among contacts during the 24 months of follow-up, ascertained using capture-recapture analysis. Microbiologically proven tuberculosis and treatment completion rates among contacts diagnosed with tuberculosis will be secondary endpoints. The incremental cost-effectiveness ratio will be estimated. The study will have 80% power to detect a 50% increase in the primary endpoint in the active intervention arm compared with the control arm. The study will include 8,829 contacts in each of the active screening and control groups, within 70 districts in 8 provinces in Vietnam, in both rural and urban settings. Discussion The effectiveness of contact investigation as a tool for improved tuberculosis case finding has not been established. This cluster randomized trial will provide valuable operational information for national tuberculosis programs in high-prevalence countries, in order to select the most cost-effective strategies to improve tuberculosis case detection. Trial registration The ACT2 study has been registered with the Australian New Zealand Clinical Trials Registry (ACTRN12610000600044).
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Affiliation(s)
- Gregory J Fox
- Woolcock Institute of Medical Research, 431 Glebe Point Road, Glebe, NSW 2037, Australia.
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Yeboah-Manu D, Asante-Poku A, Bodmer T, Stucki D, Koram K, Bonsu F, Pluschke G, Gagneux S. Genotypic diversity and drug susceptibility patterns among M. tuberculosis complex isolates from South-Western Ghana. PLoS One 2011; 6:e21906. [PMID: 21779354 PMCID: PMC3133566 DOI: 10.1371/journal.pone.0021906] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2010] [Accepted: 06/14/2011] [Indexed: 11/18/2022] Open
Abstract
Objective The aim of this study was to use spoligotyping and large sequence polymorphism (LSP) to study the population structure of M. tuberculosis complex (MTBC) isolates. Methods MTBC isolates were identified using standard biochemical procedures, IS6110 PCR, and large sequence polymorphisms. Isolates were further typed using spoligotyping, and the phenotypic drug susceptibility patterns were determined by the proportion method. Result One hundred and sixty-two isolates were characterised by LSP typing. Of these, 130 (80.25%) were identified as Mycobacterium tuberculosis sensu stricto (MTBss), with the Cameroon sub-lineage being dominant (N = 59/130, 45.38%). Thirty-two (19.75%) isolates were classified as Mycobacterium africanum type 1, and of these 26 (81.25%) were identified as West-Africa I, and 6 (18.75%) as West-Africa II. Spoligotyping sub-lineages identified among the MTBss included Haarlem (N = 15, 11.53%), Ghana (N = 22, 16.92%), Beijing (4, 3.08%), EAI (4, 3.08%), Uganda I (4, 3.08%), LAM (2, 1.54%), X (N = 1, 0.77%) and S (2, 1.54%). Nine isolates had SIT numbers with no identified sub-lineages while 17 had no SIT numbers. MTBss isolates were more likely to be resistant to streptomycin (p<0.008) and to any drug resistance (p<0.03) when compared to M. africanum. Conclusion This study demonstrated that overall 36.4% of TB in South-Western Ghana is caused by the Cameroon sub-lineage of MTBC and 20% by M. africanum type 1, including both the West-Africa 1 and West-Africa 2 lineages. The diversity of MTBC in Ghana should be considered when evaluating new TB vaccines.
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Affiliation(s)
- Dorothy Yeboah-Manu
- Noguchi Memorial Institute for Medical Research, University of Ghana, Legon, Ghana.
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Crampin A, Kasimba S, Mwaungulu NJ, Dacombe R, Floyd S, Glynn JR, Fine PEM. Married to M. tuberculosis: risk of infection and disease in spouses of smear-positive tuberculosis patients. Trop Med Int Health 2011; 16:811-8. [PMID: 21447058 PMCID: PMC3378469 DOI: 10.1111/j.1365-3156.2011.02763.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
OBJECTIVES To quantify the risk of infection and disease in spouses of tuberculosis patients and the extent to which intervention could reduce the risk in this highly exposed group. METHODS We compared HIV prevalence, TB prevalence and incidence and tuberculin skin test (TST) results in spouses of TB patients and community controls. HIV-positive spouses were offered isoniazid preventive therapy (IPT), and TST was repeated at 6, 12 and 24 months. RESULTS We recruited 148 spouses of smear-positive patients ascertained prospectively and 3% had active TB. We identified 203 spouses of previously diagnosed smear-positive patients, 11 had already had TB, and the rate of TB was 2.4 per 100 person years(py) over 2 years (95% CI 1.15-5.09). 116 were found alive and recruited. HIV prevalence was 37% and 39% in the prospective and retrospective spouse groups and 17% in controls. TST was ≥10 mm in 80% of HIV negative and in 57% of HIV-positive spouses ascertained retrospectively; 74% HIV negative and 62% HIV-positive spouses ascertained prospectively, and 48% HIV negative and 26% HIV-positive community controls. Of 54 HIV-positive spouses, 18 completed 6-month IPT. At 2 year follow-up, 87% of surviving spouses had TST ≥10 mm and the rate of TB was 1.1 per 100 py (95% CI 0.34-3.29). CONCLUSIONS Spouses are a high-risk group who should be screened for HIV and active TB. TST prevalence was already high by the time the spouses were approached but further infections were seen to occur. Uptake and adherence to IPT was disappointing, lessening the impact of short-duration therapy.
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Buu TN, van Soolingen D, Huyen MNT, Lan NNT, Quy HT, Tiemersma EW, Borgdorff MW, Cobelens FGJ. Tuberculosis acquired outside of households, rural Vietnam. Emerg Infect Dis 2010; 16:1466-8. [PMID: 20735935 PMCID: PMC3294980 DOI: 10.3201/eid1609.100281] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
Using population-based data from rural Vietnam, we assessed tuberculosis (TB) transmission within and outside of households. Eighty-three percent of persons with recent household TB were infected by different strains of Mycobacterium tuberculosis than were their household members. This result argues against the effectiveness of active TB case finding among household members.
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Affiliation(s)
- Tran N Buu
- Pham Ngoc Thach Tuberculosis and Lung Disease Hospital, Ho Chi Minh City, Vietnam
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Glynn JR, Alghamdi S, Mallard K, McNerney R, Ndlovu R, Munthali L, Houben RM, Fine PEM, French N, Crampin AC. Changes in Mycobacterium tuberculosis genotype families over 20 years in a population-based study in Northern Malawi. PLoS One 2010; 5:e12259. [PMID: 20808874 PMCID: PMC2923199 DOI: 10.1371/journal.pone.0012259] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2010] [Accepted: 07/26/2010] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND Despite increasing interest in possible differences in virulence and transmissibility between different genotypes of M. tuberculosis, very little is known about how genotypes within a population change over decades, or about relationships to HIV infection. METHODS AND PRINCIPAL FINDINGS In a population-based study in rural Malawi we have examined smears and cultures from tuberculosis patients over a 20-year period using spoligotyping. Isolates were grouped into spoligotype families and lineages following previously published criteria. Time trends, HIV status, drug resistance and outcome were examined by spoligotype family and lineage. In addition, transmissibility was examined among pairs of cases with known epidemiological contact by assessing the proportion of transmissions confirmed for each lineage, on the basis of IS6110 RFLP similarity of the M tuberculosis strains. 760 spoligotypes were obtained from smears from 518 patients from 1986-2002, and 377 spoligotypes from cultures from 347 patients from 2005-2008. There was good consistency in patients with multiple specimens. Among 781 patients with first episode tuberculosis, the majority (76%) had Lineage 4 ("European/American") strains; 9% had Lineage 3 ("East-African/Indian"); 8% Lineage 1 ("Indo-Oceanic"); and 2% Lineage 2 ("East-Asian"); others unclassifiable. Over time the proportion of Lineage 4 decreased from >90% to 60%, with an increase in the other 3 lineages (p<0.001). Lineage 1 strains were more common in those with HIV infection, even after adjusting for age, sex and year. There were no associations with drug resistance or outcome, and no differences by lineage in the proportion of pairs in which transmission was confirmed. CONCLUSIONS This is the first study to describe long term trends in the four M. tuberculosis lineages in a population. Lineage 4 has probably been longstanding in this population, with relatively recent introductions and spread of Lineages1-3, perhaps influenced by the HIV epidemic.
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Affiliation(s)
- Judith R Glynn
- London School of Hygiene & Tropical Medicine, London, United Kingdom.
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Kang SH, Park SW, Kwon KY, Hong WJ. A solitary skull lesion of syphilitic osteomyelitis. J Korean Neurosurg Soc 2010; 48:85-7. [PMID: 20717520 DOI: 10.3340/jkns.2010.48.1.85] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2010] [Revised: 04/30/2010] [Accepted: 06/14/2010] [Indexed: 11/27/2022] Open
Abstract
We experienced a rare case of solitary syphilitic osteomyelitis of the skull without any other clinical signs or symptoms of syphilis. A 20-year-old man was referred due to intermittent headache and mild tenderness at the right parietal area of the skull with a palpable coin-sized lesion of softened cortical bone. On radiological studies, the lesion was a radiolucent well enhanced mass (17 mm in diameter). The erythrocyte sedimentation rate (52 mm/h) and C-reactive protein (2.24 mg/dL) were elevated on admission. Serum venereal disease research laboratory (VDRL) and Treponema pallidum haemagglutination assay (TPHA) tests were positive. There were no clinical signs or symptoms of syphilis. After treatment with benzathine penicillin, we removed the lesion and performed cranioplasty. The pathologic finding of the skull lesion was fibrous proliferation with lymphoplasmocytic infiltration forming an osteolytic lesion. In addition, a spirochete was identified using the Warthin-starry stain. The polymerase chain reaction study showed a positive band for Treponema pallidum. Solitary osteomyelitis of the skull can be the initial presenting pathological lesion of syphilis.
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Affiliation(s)
- Suk Hyung Kang
- Department of Neurological Surgery, Yongsan Hospital, Chung-Ang University College of Medicine, Seoul, Korea
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Mulenga C, Shamputa IC, Mwakazanga D, Kapata N, Portaels F, Rigouts L. Diversity of Mycobacterium tuberculosis genotypes circulating in Ndola, Zambia. BMC Infect Dis 2010; 10:177. [PMID: 20565802 PMCID: PMC2906459 DOI: 10.1186/1471-2334-10-177] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2010] [Accepted: 06/17/2010] [Indexed: 11/10/2022] Open
Abstract
Background Tuberculosis (TB) is one of the major public health problems in Zambia. However, information about lineages of M. tuberculosis complex (MTBC) isolates useful for epidemiology investigations is unknown. In this study, we investigated the diversity of MTBC isolates from Ndola, a typical Zambian urbanized city with a documented high HIV prevalence. Methods This was part of a prospective cohort study in subjects with sputum smear-positive pulmonary TB. Spoligotyping was used to genotype the MTBC isolates and establish the circulating lineages. The 15-locus Mycobacterial Interspersed Repetitive Units - Variable Number Tandem Repeats (MIRU-VNTR) typing was used to study recent transmission. Results A total of 98 different spoligotypes were identified among 273 MTBC isolates. The majority (64.8%) of the isolates belonged to 9 known families, while 96 (35.2%) of the isolates were orphans. While LAM (41.8%) was the largest spoligotype family observed, most of the isolates (87.7%) belonging to the SAF1 family, with a significant portion coming from the T (13.6%), and X (5.9%) families. A few isolates (3.6%) belonged to the CAS, EAI, H, S, X1-LAM9 or U families. MIRU-VNTR typing was highly discriminatory (h = 0.988) among the 156 isolates tested in our sample, and increased the discrimination among 82 SAF1 isolates from 6 to 46 distinct patterns. In addition, 3.2% (5/156) of cases with available MIRU-VNTR results harbored more than one MTBC strain. Conclusions Our findings show a limited diversity of MTBC in Ndola with a high clustering rate (37.7%), which indicates that recent transmission plays an appreciable role in the dynamics of TB disease in this setting. This conclusion emphasizes the importance of early diagnosis and timely treatment. The results also confirm that MIRU-VNTR typing is suitable for studying the molecular epidemiology of TB in Ndola.
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Houben RMGJ, Crampin AC, Mallard K, Mwaungulu JN, Yates MD, Mwaungulu FD, Ngwira BMM, French N, Fine PEM, Glynn JR. HIV and the risk of tuberculosis due to recent transmission over 12 years in Karonga District, Malawi. Trans R Soc Trop Med Hyg 2009; 103:1187-9. [PMID: 19362727 PMCID: PMC2784949 DOI: 10.1016/j.trstmh.2009.03.013] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2009] [Revised: 03/11/2009] [Accepted: 03/12/2009] [Indexed: 11/30/2022] Open
Abstract
Tuberculosis (TB) patients with strains common to other recent cases (‘clustering’) suggest recent transmission. HIV status and age may affect proportions clustered. We investigated TB clustering by HIV and age in a population-based study in Malawi. Among 746 patients, HIV infection increased the proportion clustered. Sex-period-adjusted odds ratios for the association of HIV and clustering were 1.26 (95% CI 0.4–4.1) for ages 15–25 years, 1.40 (0.9–2.3) for 25–50 years and 10.44 (2.3–47.9) for >50 years and remained stable over two periods examined. These results suggest that HIV increases the proportion of TB due to recent transmission in the elderly.
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Crampin AC, Glynn JR, Fine PEM. What has Karonga taught us? Tuberculosis studied over three decades. Int J Tuberc Lung Dis 2009; 13:153-64. [PMID: 19146741 PMCID: PMC3272402] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/27/2023] Open
Abstract
This paper summarises tuberculosis (TB) research over almost 30 years in Karonga District, northern Malawi, an area typical of much of rural Africa. The dominant factor has been the human immunodeficiency virus (HIV), which arrived in the district about 1980, leading to an increase in TB incidence to a peak of approximately 65 smear-positive pulmonary cases per 100000 population in 2000. Tuberculin surveys indicate annual risks of Mycobacterium tuberculosis infection of approximately 1%; thus, most of the population is uninfected and at risk of primary infection and disease. Molecular epidemiological studies demonstrate that about two thirds of TB arises from recent infection, but recognisable recent contact is responsible for only about 10% of disease. By 2001, 57% of TB was directly attributable to HIV, implying that it would have declined were it not for HIV. HIV infection increases the risk of TB most among young adults, and greatly increases the risk of recurrence from new infection after treatment. Mortality rates in the HIV-infected are high, but there is no association of HIV with drug resistance. Other risk factors with relatively smaller effects include age and sex, contact, several genetic polymorphisms and area. Neither one nor two doses of the bacille Calmette-Guérin (BCG) vaccine provides protection against adult pulmonary TB, despite protecting against leprosy. Skin test surveys, cohort studies and comparative immunological studies with the UK suggest that exposure to environmental mycobacteria provides some protection against TB and that BCG's failure is attributable partly to this widespread heterologous exposure masking effects of the vaccine. Drug resistance has remained constant (<10%) over more than 20 years. Immunotherapy with M. vaccae provided no benefits, but treatment of HIV-positive patients with cotrimoxazole reduced mortality. The Karonga programme illustrates the value of long-term population-based studies to investigate the natural history of TB and to influence TB control policy. Current studies focus on immunological markers of infection, disease and protection, and on elucidating the impact of antiretroviral treatment on TB incidence at population level.
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Affiliation(s)
- A C Crampin
- London School of Hygiene & Tropical Medicine, London, UK.
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Effects of duration of HIV infection and secondary tuberculosis transmission on tuberculosis incidence in the South African gold mines. AIDS 2008; 22:1859-67. [PMID: 18753936 DOI: 10.1097/qad.0b013e3283097cfa] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
BACKGROUND HIV increases the risk of tuberculosis directly, through immunosuppression, and indirectly, through onward transmission of Mycobacterium tuberculosis from the increased caseload. We assess the contribution of these two mechanisms by time since seroconversion to HIV. METHODS The incidence of new pulmonary tuberculosis was estimated in a retrospective cohort study of South African gold miners over 14 years. HIV tests were done in random surveys in 1992-1993, and in clinics. One thousand nine hundred fifty HIV positive men with seroconversion intervals of less than 3 years were identified and linked to medical, demographic and occupational records. They were compared with men who were HIV-negative in a survey, with no later evidence of HIV. Analyses were censored when men were diagnosed with tuberculosis, died or left the mine. RESULTS Tuberculosis incidence rose soon after HIV infection, reaching 1.4/100 person-years (95% confidence interval 1.1-1.9) within 2 years, and 10.0/100 person-years (95% confidence interval 6.5-15.5) at 10 or more years. By 11 years from seroconversion, nearly half the men had had tuberculosis. Among 5702 HIV-negative men, tuberculosis incidence was 0.48/100 person-years (95% confidence interval 0.33-0.70) in 1991-1993 and doubled over the period of the study (after adjusting for age). Age-adjusted model estimates suggest that half the increase in tuberculosis incidence by time since HIV infection was attributable to increasing incidence over calendar period--the indirect effect. CONCLUSION For the first time, we have shown that the increase in tuberculosis risk by time since seroconversion reflects both direct effects of HIV increasing susceptibility, and indirect effects due to onward transmission. Innovative and sustained public health measures are needed to reduce Mycobacterium tuberculosis transmission.
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Crampin AC, Floyd S, Ngwira BM, Mwinuka V, Mwaungulu JN, Branson K, Fine PEM, Glynn JR. Assessment and evaluation of contact as a risk factor for tuberculosis in rural Africa. Int J Tuberc Lung Dis 2008; 12:612-618. [PMID: 18492326 PMCID: PMC2443279] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/26/2023] Open
Abstract
SETTING A rural district in Malawi. OBJECTIVE To determine the effect of inaccurate recall on estimates of the proportion of tuberculosis (TB) cases attributable to contact with identifiable prior cases. DESIGN Case-control study of laboratory-confirmed TB cases and community controls, comparing family, household and area contacts identified from a database of TB cases with those named at interview. Estimation of prior contact as a risk factor for TB and identified factors associated with being a named contact. RESULTS Ninety-five per cent of named contacts were known TB cases. The proportion of total identified contacts who were named at interview was 75%, and was similar for cases and controls. Cases were twice as likely as controls to identify prior contacts. Adding database information did not affect odds ratios, but increased the proportion of TB cases attributable to prior contact. Smear-positive, male and human immunodeficiency virus (HIV) negative TB patients were more likely to be named by subsequent cases. Identifiable recent contact with known smear-positive cases accounted for 12.5% of the TB burden. CONCLUSIONS Reporting of putative source contacts showed little evidence of recall bias and gave estimates of the relative risk of TB associated with identifiable contact. The lower likelihood of HIV-positive cases being named as contacts may reflect reduced infectiousness.
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DeRiemer K, Kawamura LM, Hopewell PC, Daley CL. Quantitative impact of human immunodeficiency virus infection on tuberculosis dynamics. Am J Respir Crit Care Med 2007; 176:936-44. [PMID: 17690336 PMCID: PMC2048673 DOI: 10.1164/rccm.200603-440oc] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
RATIONALE Human immunodeficiency virus (HIV) infection has a major but unquantified impact on the risk of tuberculosis. OBJECTIVES To quantify the impact of HIV infection on the number of tuberculosis cases in San Francisco. METHODS We studied all patients reported with tuberculosis in San Francisco from 1991 to 2002. The initial isolates of Mycobacterium tuberculosis were genotyped using IS6110 restriction fragment-length polymorphism genotyping as the primary method, and clustered cases (identical genotype patterns) were identified. MEASUREMENTS AND MAIN RESULTS We determined the case number, case rate, and the fraction of tuberculosis attributable to HIV infection. Of 2,991 reported tuberculosis cases, 2,193 (73.3%) had a genotype pattern of M. tuberculosis available. Genotypic clusters with at least one HIV-positive person were larger, lasted longer, and had a shorter time between successive cases relative to clusters with only HIV-uninfected persons (P < 0.00005, P = 0.0009, P = 0.018, respectively). Overall, 13.7% of the tuberculosis cases were attributable to HIV infection and an estimated 405 excess tuberculosis cases occurred. CONCLUSIONS During a period encompassing the resurgence and decline of tuberculosis in San Francisco, a substantial number of the tuberculosis cases were attributable to HIV infection. Coinfection with HIV amplified the local tuberculosis epidemic.
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Affiliation(s)
- Kathryn DeRiemer
- School of Medicine, University of California, Davis, California 95616, USA.
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