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Mingotti N, Grogono D, Dello Ioio G, Curran M, Barbour K, Taveira M, Rudman J, Haworth CS, Floto RA, Woods AW. The Impact of Hospital-Ward Ventilation on Airborne-Pathogen Exposure. Am J Respir Crit Care Med 2021; 203:766-769. [PMID: 33211973 DOI: 10.1164/rccm.202009-3634le] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Affiliation(s)
| | - Dorothy Grogono
- University of Cambridge Cambridge, United Kingdom.,Royal Papworth Hospital Cambridge, United Kingdom.,Cambridge Infectious Diseases Interdisciplinary Research Centre Cambridge, United Kingdom and
| | | | - Martin Curran
- Cambridge University Hospitals Cambridge, United Kingdom
| | | | | | - Josie Rudman
- Royal Papworth Hospital Cambridge, United Kingdom
| | - Charles S Haworth
- University of Cambridge Cambridge, United Kingdom.,Royal Papworth Hospital Cambridge, United Kingdom
| | - R Andres Floto
- University of Cambridge Cambridge, United Kingdom.,Royal Papworth Hospital Cambridge, United Kingdom.,Cambridge Infectious Diseases Interdisciplinary Research Centre Cambridge, United Kingdom and
| | - Andrew W Woods
- University of Cambridge Cambridge, United Kingdom.,Cambridge Infectious Diseases Interdisciplinary Research Centre Cambridge, United Kingdom and
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2
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Nordsiek F, Bodenschatz E, Bagheri G. Risk assessment for airborne disease transmission by poly-pathogen aerosols. PLoS One 2021; 16:e0248004. [PMID: 33831003 PMCID: PMC8031403 DOI: 10.1371/journal.pone.0248004] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2020] [Accepted: 02/17/2021] [Indexed: 02/03/2023] Open
Abstract
In the case of airborne diseases, pathogen copies are transmitted by droplets of respiratory tract fluid that are exhaled by the infectious that stay suspended in the air for some time and, after partial or full drying, inhaled as aerosols by the susceptible. The risk of infection in indoor environments is typically modelled using the Wells-Riley model or a Wells-Riley-like formulation, usually assuming the pathogen dose follows a Poisson distribution (mono-pathogen assumption). Aerosols that hold more than one pathogen copy, i.e. poly-pathogen aerosols, break this assumption even if the aerosol dose itself follows a Poisson distribution. For the largest aerosols where the number of pathogen in each aerosol can sometimes be several hundred or several thousand, the effect is non-negligible, especially in diseases where the risk of infection per pathogen is high. Here we report on a generalization of the Wells-Riley model and dose-response models for poly-pathogen aerosols by separately modeling each number of pathogen copies per aerosol, while the aerosol dose itself follows a Poisson distribution. This results in a model for computational risk assessment suitable for mono-/poly-pathogen aerosols. We show that the mono-pathogen assumption significantly overestimates the risk of infection for high pathogen concentrations in the respiratory tract fluid. The model also includes the aerosol removal due to filtering by the individuals which becomes significant for poorly ventilated environments with a high density of individuals, and systematically includes the effects of facemasks in the infectious aerosol source and sink terms and dose calculations.
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Affiliation(s)
- Freja Nordsiek
- Max Planck Institute for Dynamics and Self-Organization (MPIDS), Göttingen, Niedersachsen, Germany
| | - Eberhard Bodenschatz
- Max Planck Institute for Dynamics and Self-Organization (MPIDS), Göttingen, Niedersachsen, Germany
- Institute for Dynamics of Complex Systems, University of Göttingen, Göttingen, Niedersachsen, Germany
- Laboratory of Atomic and Solid State Physics and Sibley School of Mechanical and Aerospace Engineering, Cornell University, Ithaca, New York, United States of America
| | - Gholamhossein Bagheri
- Max Planck Institute for Dynamics and Self-Organization (MPIDS), Göttingen, Niedersachsen, Germany
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3
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Agarwal A, Fernando SM, Honarmand K, Bakaa L, Brar S, Granton D, Chaudhuri D, Chetan D, Hu M, Basmaji J, Muttalib F, Rochwerg B, Adhikari NKJ, Lamontagne F, Murthy S, Hui DS, Gomersall CD, Mubareka S, Diaz J, Burns KE, Couban R, Vandvik PO. Risk of dispersion or aerosol generation and infection transmission with nasopharyngeal and oropharyngeal swabs for detection of COVID-19: a systematic review. BMJ Open 2021; 11:e040616. [PMID: 33737418 PMCID: PMC7977073 DOI: 10.1136/bmjopen-2020-040616] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
OBJECTIVES SARS-CoV-2-related disease, referred to as COVID-19, has emerged as a global pandemic since December 2019. While there is growing recognition regarding possible airborne transmission, particularly in the setting of aerosol-generating procedures and treatments, whether nasopharyngeal and oropharyngeal swabs for SARS-CoV-2 generate aerosols remains unclear. DESIGN Systematic review. DATA SOURCES We searched Ovid MEDLINE and EMBASE up to 3 November 2020. We also searched the China National Knowledge Infrastructure, Chinese Medical Journal Network, medRxiv and ClinicalTrials.gov up to 29 March 2020. ELIGIBILITY CRITERIA All comparative and non-comparative studies that evaluated dispersion or aerosolisation of viable airborne organisms, or transmission of infection associated with nasopharyngeal or oropharyngeal swab testing. RESULTS Of 7702 citations, only one study was deemed eligible. Using a dedicated sampling room with negative pressure isolation room, personal protective equipment including N95 or higher masks, strict sterilisation protocols, structured training with standardised collection methods and a structured collection and delivery system, a tertiary care hospital proved a 0% healthcare worker infection rate among eight nurses conducting over 11 000 nasopharyngeal swabs. No studies examining transmissibility with other safety protocols, nor any studies quantifying the risk of aerosol generation with nasopharyngeal or oropharyngeal swabs for detection of SARS-CoV-2, were identified. CONCLUSIONS There is limited to no published data regarding aerosol generation and risk of transmission with nasopharyngeal and oropharyngeal swabs for the detection of SARS-CoV-2. Field experiments to quantify this risk are warranted. Vigilance in adhering to current standards for infection control is suggested.
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Affiliation(s)
- Arnav Agarwal
- Department of Medicine, University of Toronto, Toronto, Ontario, Canada
- Department of Health Research Methods, Evidence and Impact, McMaster University, Hamilton, Ontario, Canada
| | - Shannon M Fernando
- Division of Critical Care, Department of Medicine, University of Ottawa, Ottawa, Ontario, Canada
- Department of Emergency Medicine, University of Ottawa, Ottawa, Ontario, Canada
| | - Kimia Honarmand
- Division of Critical Care, Department of Medicine, Western University, London, Ontario, Canada
| | - Layla Bakaa
- Faculty of Science, McMaster University, Hamilton, Ontario, Canada
| | - Sonia Brar
- School of Medicine and Biomedical Sciences, University of Buffalo, Buffalo, New York, USA
| | - David Granton
- Michael G. DeGroote School of Medicine, McMaster University, Hamilton, Ontario, Canada
| | - Dipayan Chaudhuri
- Department of Medicine, McMaster University, Hamilton, Ontario, Canada
| | - Devin Chetan
- Department of Pediatrics, University of Toronto, Toronto, Ontario, Canada
- Division of Cardiology, Labatt Family Heart Centre, Hospital for Sick Children, Toronto, Ontario, Canada
| | - Malini Hu
- Michael G. DeGroote School of Medicine, McMaster University, Hamilton, Ontario, Canada
| | - John Basmaji
- Division of Critical Care, Department of Medicine, Western University, London, Ontario, Canada
| | - Fiona Muttalib
- Center for Global Child Health, Hospital for Sick Children, Toronto, Ontario, Canada
| | - Bram Rochwerg
- Department of Health Research Methods, Evidence and Impact, McMaster University, Hamilton, Ontario, Canada
- Michael G. DeGroote School of Medicine, McMaster University, Hamilton, Ontario, Canada
| | - Neill K J Adhikari
- Department of Critical Care Medicine, Sunnybrook Health Sciences Centre, Toronto, Ontario, Canada
- Interdepartmental Division of Critical Care Medicine, University of Toronto, Toronto, Ontario, Canada
| | - Francois Lamontagne
- Centre de recherche due CHU de Sherbrooke, Université de Sherbrooke, Sherbrooke, Quebec, Canada
- Département de Médecine, Université de Sherbrooke, Sherbrooke, Quebec, Canada
| | - Srinivas Murthy
- Faculty of Medicine, BC Children's Hospital, University of British Columbia, Vancouver, British Columbia, Canada
| | - David S Hui
- Department of Medicine and Therapeutics, Chinese University of Hong Kong, Shatin, Hong Kong
- Stanley Ho Center for Emerging Infectious Diseases, Chinese University of Hong Kong, Shatin, Hong Kong
| | - Charles D Gomersall
- Department of Anaesthesia and Intensive Care, Chinese University of Hong Kong, Shatin, Hong Kong
| | - Samira Mubareka
- Division of Infectious Diseases, University of Toronto, Toronto, Ontario, Canada
- Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Ontario, Canada
| | - Janet Diaz
- Pacific Medical Center, San Francisco, California, USA
- World Health Organization, Geneva, Switzerland
| | - Karen Ea Burns
- Interdepartmental Division of Critical Care Medicine, University of Toronto, Toronto, Ontario, Canada
- Division of Critical Care, Unity Health Toronto - St. Michael's Hospital, Toronto, Ontario, Canada
- Li Ka Shing Knowledge Institute, Unity Health Toronto - St. Michael's Hospital, Toronto, Ontario, Canada
| | - Rachel Couban
- Department of Health Research Methods, Evidence and Impact, McMaster University, Hamilton, Ontario, Canada
- Michael G. DeGroote Institute for Pain Research and Care, McMaster University, Hamilton, Ontario, Canada
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4
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Harrichandra A, Ierardi AM, Pavilonis B. An estimation of airborne SARS-CoV-2 infection transmission risk in New York City nail salons. Toxicol Ind Health 2020; 36:634-643. [PMID: 33085569 PMCID: PMC7578841 DOI: 10.1177/0748233720964650] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2020] [Revised: 01/10/2020] [Accepted: 09/16/2020] [Indexed: 01/13/2023]
Abstract
Although airborne transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) from person-to-person over long distances is currently thought to be unlikely, the current epidemiological evidence suggests that airborne SARS-CoV-2 infection transmission in confined, indoor spaces is plausible, particularly when outdoor airflow rates are low and when face masks are not utilized. We sought to model airborne infection transmission risk assuming five realistic exposure scenarios using previously estimated outdoor airflow rates for 12 New York City nail salons, a published quanta generation rate specific to SARS-CoV-2, as well as the Wells-Riley equation to assess risk under both steady-state and non-steady-state conditions. Additionally, the impact of face mask-wearing by occupants on airborne infection transmission risk was also evaluated. The risk of airborne infection transmission across all salons and all exposure scenarios when not wearing face masks ranged from <0.015% to 99.25%, with an average airborne infection transmission risk of 24.77%. Wearing face masks reduced airborne infection transmission risk to between <0.01% and 51.96%, depending on the salon, with an average airborne infection transmission risk of 7.30% across all salons. Increased outdoor airflow rates in nail salons were generally strongly correlated with decreased average airborne infection transmission risk. The results of this study indicate that increased outdoor airflow rates and the use of face masks by both employees and customers could substantially reduce SARS-CoV-2 transmission in New York City nail salons. Businesses should utilize multiple layers of infection control measures (e.g. social distancing, face masks, and outdoor airflow) to reduce airborne infection transmission risk for both employees and customers.
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Affiliation(s)
- Amelia Harrichandra
- Department of Environmental, Occupational, and Geospatial Health Sciences, City University of New York Graduate School of Public Health and Health Policy, New York, NY, USA
| | - A Michael Ierardi
- Department of Environmental, Occupational, and Geospatial Health Sciences, City University of New York Graduate School of Public Health and Health Policy, New York, NY, USA
- Cardno ChemRisk, Brooklyn, NY, USA
| | - Brian Pavilonis
- Department of Environmental, Occupational, and Geospatial Health Sciences, City University of New York Graduate School of Public Health and Health Policy, New York, NY, USA
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5
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Fennelly KP. Particle sizes of infectious aerosols: implications for infection control. THE LANCET. RESPIRATORY MEDICINE 2020; 8:914-924. [PMID: 32717211 PMCID: PMC7380927 DOI: 10.1016/s2213-2600(20)30323-4] [Citation(s) in RCA: 320] [Impact Index Per Article: 80.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/29/2020] [Revised: 07/06/2020] [Accepted: 07/08/2020] [Indexed: 12/13/2022]
Abstract
The global pandemic of COVID-19 has been associated with infections and deaths among health-care workers. This Viewpoint of infectious aerosols is intended to inform appropriate infection control measures to protect health-care workers. Studies of cough aerosols and of exhaled breath from patients with various respiratory infections have shown striking similarities in aerosol size distributions, with a predominance of pathogens in small particles (<5 μm). These are immediately respirable, suggesting the need for personal respiratory protection (respirators) for individuals in close proximity to patients with potentially virulent pathogens. There is no evidence that some pathogens are carried only in large droplets. Surgical masks might offer some respiratory protection from inhalation of infectious aerosols, but not as much as respirators. However, surgical masks worn by patients reduce exposures to infectious aerosols to health-care workers and other individuals. The variability of infectious aerosol production, with some so-called super-emitters producing much higher amounts of infectious aerosol than most, might help to explain the epidemiology of super-spreading. Airborne infection control measures are indicated for potentially lethal respiratory pathogens such as severe acute respiratory syndrome coronavirus 2.
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Affiliation(s)
- Kevin P Fennelly
- Pulmonary Branch, Division of Intramural Research, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD, USA.
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6
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Su CP, de Perio MA, Cummings KJ, McCague AB, Luckhaupt SE, Sweeney MH. Case Investigations of Infectious Diseases Occurring in Workplaces, United States, 2006-2015. Emerg Infect Dis 2019; 25:397-405. [PMID: 30789129 PMCID: PMC6390751 DOI: 10.3201/eid2503.180708] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Workers in specific settings and activities are at increased risk for certain infectious diseases. When an infectious disease case occurs in a worker, investigators need to understand the mechanisms of disease propagation in the workplace. Few publications have explored these factors in the United States; a literature search yielded 66 investigations of infectious disease occurring in US workplaces during 2006–2015. Reported cases appear to be concentrated in specific industries and occupations, especially the healthcare industry, laboratory workers, animal workers, and public service workers. A hierarchy-of-controls approach can help determine how to implement effective preventive measures in workplaces. Consideration of occupational risk factors and control of occupational exposures will help prevent disease transmission in the workplace and protect workers’ health.
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7
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Patterson B, Morrow C, Singh V, Moosa A, Gqada M, Woodward J, Mizrahi V, Bryden W, Call C, Patel S, Warner D, Wood R. Detection of Mycobacterium tuberculosis bacilli in bio-aerosols from untreated TB patients. Gates Open Res 2018; 1:11. [PMID: 29355225 PMCID: PMC5757796 DOI: 10.12688/gatesopenres.12758.2] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/05/2018] [Indexed: 12/02/2022] Open
Abstract
Background: Tuberculosis (TB) is predominantly an airborne disease. However, quantitative and qualitative analysis of bio-aerosols containing the aetiological agent,
Mycobacterium tuberculosis (Mtb), has proven very challenging. Our objective is to sample bio-aerosols from newly diagnosed TB patients for detection and enumeration of
Mtb bacilli. Methods: We monitored each of 35 newly diagnosed, GeneXpert sputum-positive, TB patients during 1 hour confinement in a custom-built Respiratory Aerosol Sampling Chamber (RASC). The RASC (a small clean-room of 1.4m
) incorporates aerodynamic particle size detection, viable and non-viable sampling devices, real-time CO
2 monitoring, and cough sound-recording. Microbiological culture and droplet digital polymerase chain reaction (ddPCR) were used to detect
Mtb in each of the bio-aerosol collection devices. Results:
Mtb was detected in 27/35 (77.1%) of aerosol samples; 15/35 (42.8%) samples were positive by mycobacterial culture and 25/27 (92.96%) were positive by ddPCR. Culturability of collected bacilli was not predicted by radiographic evidence of pulmonary cavitation, sputum smear positivity. A correlation was found between cough rate and culturable bioaerosol.
Mtb was detected on all viable cascade impactor stages with a peak at aerosol sizes 2.0-3.5μm. This suggests a median of 0.09 CFU/litre of exhaled air (IQR: 0.07 to 0.3 CFU/l) for the aerosol culture positives and an estimated median concentration of 4.5x10
CFU/ml (IQR: 2.9x10
-5.6x10
) of exhaled particulate bio-aerosol. Conclusions:
Mtb was identified in bio-aerosols exhaled by the majority of untreated TB patients using the RASC. Molecular detection was more sensitive than mycobacterial culture on solid media, suggesting that further studies are required to determine whether this reflects a significant proportion of differentially detectable bacilli in these samples.
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Affiliation(s)
- Benjamin Patterson
- Division of Infectious Diseases, Department of Medicine, Columbia University, College of Physicians and Surgeons, New York, NY, USA
| | - Carl Morrow
- 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
| | - Vinayak Singh
- Institute of Infectious Disease and Molecular Medicine (IDM), Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa.,MRC/NHLS/UCT Molecular Mycobacteriology Research Unit & DST/NRF Centre of Excellence for Biomedical TB Research, Department of Pathology, Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa
| | - Atica Moosa
- Institute of Infectious Disease and Molecular Medicine (IDM), Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa.,MRC/NHLS/UCT Molecular Mycobacteriology Research Unit & DST/NRF Centre of Excellence for Biomedical TB Research, Department of Pathology, 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
| | - Jeremy Woodward
- Department of Integrative Biomedical Sciences, Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa
| | - Valerie Mizrahi
- Institute of Infectious Disease and Molecular Medicine (IDM), Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa.,MRC/NHLS/UCT Molecular Mycobacteriology Research Unit & DST/NRF Centre of Excellence for Biomedical TB Research, Department of Pathology, Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa
| | | | | | - Shwetak Patel
- Computer Science and Engineering, Electrical Engineering DUB group, University of Washington, Seattle, USA
| | - Digby Warner
- Institute of Infectious Disease and Molecular Medicine (IDM), Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa.,MRC/NHLS/UCT Molecular Mycobacteriology Research Unit & DST/NRF Centre of Excellence for Biomedical TB Research, Department of Pathology, 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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8
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Patterson B, Morrow C, Singh V, Moosa A, Gqada M, Woodward J, Mizrahi V, Bryden W, Call C, Patel S, Warner D, Wood R. Detection of Mycobacterium tuberculosis bacilli in bio-aerosols from untreated TB patients. Gates Open Res 2018; 1:11. [PMID: 29355225 DOI: 10.12688/gatesopenres.12758.1] [Citation(s) in RCA: 45] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/30/2017] [Indexed: 11/20/2022] Open
Abstract
Background: Tuberculosis (TB) is predominantly an airborne disease. However, quantitative and qualitative analysis of bio-aerosols containing the aetiological agent, Mycobacterium tuberculosis (Mtb), has proven very challenging. Our objective is to sample bio-aerosols from newly diagnosed TB patients for detection and enumeration of Mtb bacilli. Methods: We monitored each of 35 newly diagnosed, GeneXpert sputum-positive, TB patients during 1 hour confinement in a custom-built Respiratory Aerosol Sampling Chamber (RASC). The RASC (a small clean-room of 1.4m ) incorporates aerodynamic particle size detection, viable and non-viable sampling devices, real-time CO 2 monitoring, and cough sound-recording. Microbiological culture and droplet digital polymerase chain reaction (ddPCR) were used to detect Mtb in each of the bio-aerosol collection devices. Results: Mtb was detected in 27/35 (77.1%) of aerosol samples; 15/35 (42.8%) samples were positive by mycobacterial culture and 25/27 (92.96%) were positive by ddPCR. Culturability of collected bacilli was not predicted by radiographic evidence of pulmonary cavitation, sputum smear positivity. A correlation was found between cough rate and culturable bioaerosol. Mtb was detected on all viable cascade impactor stages with a peak at aerosol sizes 2.0-3.5μm. This suggests a median of 0.09 CFU/litre of exhaled air (IQR: 0.07 to 0.3 CFU/l) for the aerosol culture positives and an estimated median concentration of 4.5x10 CFU/ml (IQR: 2.9x10 -5.6x10 ) of exhaled particulate bio-aerosol. Conclusions: Mtb was identified in bio-aerosols exhaled by the majority of untreated TB patients using the RASC. Molecular detection was more sensitive than mycobacterial culture on solid media, suggesting that further studies are required to determine whether this reflects a significant proportion of differentially detectable bacilli in these samples.
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Affiliation(s)
- Benjamin Patterson
- Division of Infectious Diseases, Department of Medicine, Columbia University, College of Physicians and Surgeons, New York, NY, USA
| | - Carl Morrow
- 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
| | - Vinayak Singh
- Institute of Infectious Disease and Molecular Medicine (IDM), Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa.,MRC/NHLS/UCT Molecular Mycobacteriology Research Unit & DST/NRF Centre of Excellence for Biomedical TB Research, Department of Pathology, Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa
| | - Atica Moosa
- Institute of Infectious Disease and Molecular Medicine (IDM), Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa.,MRC/NHLS/UCT Molecular Mycobacteriology Research Unit & DST/NRF Centre of Excellence for Biomedical TB Research, Department of Pathology, 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
| | - Jeremy Woodward
- Department of Integrative Biomedical Sciences, Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa
| | - Valerie Mizrahi
- Institute of Infectious Disease and Molecular Medicine (IDM), Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa.,MRC/NHLS/UCT Molecular Mycobacteriology Research Unit & DST/NRF Centre of Excellence for Biomedical TB Research, Department of Pathology, Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa
| | | | | | - Shwetak Patel
- Computer Science and Engineering, Electrical Engineering DUB group, University of Washington, Seattle, USA
| | - Digby Warner
- Institute of Infectious Disease and Molecular Medicine (IDM), Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa.,MRC/NHLS/UCT Molecular Mycobacteriology Research Unit & DST/NRF Centre of Excellence for Biomedical TB Research, Department of Pathology, 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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9
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Turner RD, Chiu C, Churchyard GJ, Esmail H, Lewinsohn DM, Gandhi NR, Fennelly KP. Tuberculosis Infectiousness and Host Susceptibility. J Infect Dis 2017; 216:S636-S643. [PMID: 29112746 PMCID: PMC5853924 DOI: 10.1093/infdis/jix361] [Citation(s) in RCA: 53] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
The transmission of tuberculosis is complex. Necessary factors include a source case with respiratory disease that has developed sufficiently for Mycobacterium tuberculosis to be present in the airways. Viable bacilli must then be released as an aerosol via the respiratory tract of the source case. This is presumed to occur predominantly by coughing but may also happen by other means. Airborne bacilli must be capable of surviving in the external environment before inhalation into a new potential host-steps influenced by ambient conditions and crowding and by M. tuberculosis itself. Innate and adaptive host defenses will then influence whether new infection results; a process that is difficult to study owing to a paucity of animal models and an inability to measure infection directly. This review offers an overview of these steps and highlights the many gaps in knowledge that remain.
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Affiliation(s)
| | - Christopher Chiu
- Section of Infectious Diseases & Immunity, Imperial College London, United Kingdom
| | - Gavin J Churchyard
- Aurum Institute and
- School of Public Health, University of Witwatersrand, Johannesburg, South Africa
| | - Hanif Esmail
- Radcliffe Department of Medicine, University of Oxford, United Kingdom
- Wellcome Center for Infectious Diseases Research in Africa, University of Cape Town, South Africa
| | - David M Lewinsohn
- Department of Molecular Microbiology and Immunology, Oregon Health & Science University, Portland
| | - Neel R Gandhi
- School of Medicine and Rollins School of Public Health, Emory University, Atlanta, Georgia
| | - Kevin P Fennelly
- Pulmonary Clinical Medicine Section, Cardiovascular Pulmonary Branch, Division of Intramural Research, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland
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10
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Mbugi EV, Katale BZ, Lupindu AM, Keyyu JD, Kendall SL, Dockrell HM, Michel AL, Matee MI, van Helden PD. Tuberculosis Infection: Occurrence and Risk Factors in Presumptive Tuberculosis Patients of the Serengeti Ecosystem in Tanzania. East Afr Health Res J 2017; 1:19-30. [PMID: 34308155 PMCID: PMC8279301 DOI: 10.24248/eahrj-d-16-00319] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2016] [Accepted: 02/01/2017] [Indexed: 11/20/2022] Open
Abstract
Background Cross-species tuberculosis (TB) transmission between humans and animals has been reported for quite a long time in sub-Saharan Africa. Because humans and animals coexist in the same ecosystem, exploring their potential for cross-species transmission and the impact the disease may have on the health of humans, animals, and their products is critical. Objectives This study aimed to identify risk factors for transmission of TB (Mycobacterium tuberculosis) and to assess the potential for zoonotic TB (Mycobacterium bovis) transmission in the Serengeti ecosystem where humans and animals are in intense contact. Our aim is to create a base for future implementation of appropriate control strategies to limit infection in both humans and animals. Methodology We administered a semi-structured questionnaire to 421 self-reporting patients to gather information on risk factors and TB occurrence. In a parallel study, researchers screened sputum smears using Ziehl-Neelsen staining and confirmed by mycobacterial culture. We then performed descriptive statistics (Pearson's chi-square test) and logistic regression analysis to establish frequencies, association, and quantification of the risk factors associated with TB cases. Results Our findings showed 44% (95% confidence interval [CI], 0.40-0.49) of the results were positive from sputum samples collected over a 1-year duration in areas with a high TB burden, particularly the Bunda district, followed by the Serengeti and Ngorongoro districts. Of the culture-positive patients who also had infections other than TB (43/187 patients), 21 (49%) were HIV positive. Contact with livestock products (odds ratio [OR] 6.0; 95% CI, 1.81-19.9), infrequent milk consumption (OR 2.5; 95% CI, 1.42-4.23), cigarette smoking (OR 2.9; 95% CI, 1.19-7.1.2), and alcohol consumption (OR 2.3; 95% CI, 1.22-4.23) were associated with a higher likelihood of TB infection. Conclusion There was no evidence of direct cross-species transmission of either M tuberculosis or M bovis between humans and animals using the study methods. The absence of cross-species TB transmission could be due to limited chances of contact rather than an inability of cross-species disease transmission. In addition, not all people with presumptive TB are infected with TB, and therefore control strategies should emphasise confirming TB status before administering anti-TB drugs.
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Affiliation(s)
- Erasto V Mbugi
- Department of Biochemistry, Muhimbili University of Health and Allied Sciences, Dar es Salaam, Tanzania.,Departments of Microbiology and Immunology, Muhimbili University of Health and Allied Sciences, Dar es Salaam, Tanzania
| | - Bugwesa Z Katale
- Departments of Microbiology and Immunology, Muhimbili University of Health and Allied Sciences, Dar es Salaam, Tanzania.,Tanzania Wildlife Research Institute, Arusha, Tanzania
| | - Athumani M Lupindu
- Department of Veterinary Medicine and Public Health, Sokoine University of Agriculture, Morogoro, Tanzania
| | | | | | - Hazel M Dockrell
- Department of Immunology and Infection, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - Anita L Michel
- Department of Veterinary Tropical Diseases, University of Pretoria, Pretoria, South Africa
| | - Mecky I Matee
- Departments of Microbiology and Immunology, Muhimbili University of Health and Allied Sciences, Dar es Salaam, Tanzania
| | - Paul D van Helden
- DST/NRF Centre of Excellence for Biomedical Tuberculosis Research/Medical Research Council, Centre for Molecular and Cellular Biology, Stellenbosch University, Tygerberg, South Africa
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11
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Nardell EA. Transmission and Institutional Infection Control of Tuberculosis. Cold Spring Harb Perspect Med 2015; 6:a018192. [PMID: 26292985 DOI: 10.1101/cshperspect.a018192] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Tuberculosis (TB) transmission control in institutions is evolving with increased awareness of the rapid impact of treatment on transmission, the importance of the unsuspected, untreated case of transmission, and the advent of rapid molecular diagnostics. With active case finding based on cough surveillance and rapid drug susceptibility testing, in theory, it is possible to be reasonably sure that no patient enters a facility with undiagnosed TB or drug resistance. Droplet nuclei transmission of TB is reviewed with an emphasis on risk factors relevant to control. Among environmental controls, natural ventilation and upper-room ultraviolet germicidal ultraviolet air disinfection are the most cost-effective choices, although high-volume mechanical ventilation can also be used. Room air cleaners are generally not recommended. Maintenance is required for all engineering solutions. Finally, personal protection with fit-tested respirators is used in many situations where administrative and engineering methods cannot assure protection.
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Affiliation(s)
- Edward A Nardell
- Division of Global Health Equity, Brigham & Women's Hospital, Boston, Massachusetts 02115
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12
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Or P, Chung J, Wong T. Does Training in Performing a Fit Check Enhance N95 Respirator Efficacy?. Workplace Health Saf 2012. [DOI: 10.3928/21650799-20121128-76] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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13
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Wind-driven roof turbines: a novel way to improve ventilation for TB infection control in health facilities. PLoS One 2012; 7:e29589. [PMID: 22253742 PMCID: PMC3253793 DOI: 10.1371/journal.pone.0029589] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2011] [Accepted: 11/30/2011] [Indexed: 11/26/2022] Open
Abstract
Objective Tuberculosis transmission in healthcare facilities contributes significantly to the TB epidemic, particularly in high HIV settings. Although improving ventilation may reduce transmission, there is a lack of evidence to support low-cost practical interventions. We assessed the efficacy of wind-driven roof turbines to achieve recommended ventilation rates, compared to current recommended practices for natural ventilation (opening windows), in primary care clinic rooms in Khayelitsha, South Africa. Methods Room ventilation was assessed (CO2 gas tracer technique) in 4 rooms where roof turbines and air-intake grates were installed, across three scenarios: turbine, grate and window closed, only window open, and only turbine and grate open, with concurrent wind speed measurement. 332 measurements were conducted over 24 months. Findings For all 4 rooms combined, median air changes per hour (ACH) increased with wind speed quartiles across all scenarios. Higher median ACH were recorded with open roof turbines and grates, compared to open windows across all wind speed quartiles. Ventilation with open turbine and grate exceeded WHO-recommended levels (60 Litres/second/patient) for 95% or more of measurements in 3 of the 4 rooms; 47% in the remaining room, where wind speeds were lower and a smaller diameter turbine was installed. Conclusion High room ventilation rates, meeting recommended thresholds, may be achieved using wind-driven roof turbines and grates, even at low wind speeds. Roof turbines and air-intake grates are not easily closed by staff, allowing continued ventilation through colder periods. This simple, low-cost technology represents an important addition to our tools for TB infection control.
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14
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Knibbs LD, Morawska L, Bell SC, Grzybowski P. Room ventilation and the risk of airborne infection transmission in 3 health care settings within a large teaching hospital. Am J Infect Control 2011; 39:866-72. [PMID: 21658810 PMCID: PMC7115323 DOI: 10.1016/j.ajic.2011.02.014] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2010] [Revised: 02/11/2011] [Accepted: 02/11/2011] [Indexed: 11/24/2022]
Abstract
BACKGROUND Room ventilation is a key determinant of airborne disease transmission. Despite this, ventilation guidelines in hospitals are not founded on robust scientific evidence related to the prevention of airborne transmission. METHODS We sought to assess the effect of ventilation rates on influenza, tuberculosis, and rhinovirus infection risk within 3 distinct rooms in a major urban hospital: a lung function laboratory, an emergency department negative-pressure isolation room, and an outpatient consultation room. Air-exchange rate measurements were performed in each room using CO2 as a tracer. The model developed by Gammaitoni and Nucci was used to estimate infection risk. RESULTS Current outdoor air-exchange rates in the lung function laboratory and emergency department isolation room limited infection risks to 0.1%-3.6%. Influenza risk for individuals entering an outpatient consultation room after an infectious individual departed ranged from 3.6% to 20.7%, depending on the duration for which each person occupied the room. CONCLUSION Given the absence of definitive ventilation guidelines for hospitals, air-exchange measurements combined with modeling afford a useful means of assessing, on a case-by-case basis, the suitability of room ventilation for preventing airborne disease transmission.
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Affiliation(s)
- Luke D Knibbs
- International Laboratory for Air Quality and Health, Queensland University of Technology, Brisbane, Australia
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15
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Affiliation(s)
- Daphne Ling
- Respiratory Epidemiology & Clinical Research Unit, Montreal Chest Institute, McGill University, Montreal, QC H2X 2P4, Canada
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16
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Au SSW, Gomersall CD, Leung P, Li PTY. A randomised controlled pilot study to compare filtration factor of a novel non-fit-tested high-efficiency particulate air (HEPA) filtering facemask with a fit-tested N95 mask. J Hosp Infect 2010; 76:23-5. [PMID: 20359769 PMCID: PMC7114828 DOI: 10.1016/j.jhin.2010.01.017] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2009] [Accepted: 01/13/2010] [Indexed: 11/16/2022]
Abstract
Use of a fit-tested N95 or FFP2 mask is recommended to protect against transmission of airborne pathogens. This poses considerable logistic problems when preparing for, or dealing with, an epidemic. Some of these problems might be overcome by use of a compact reusable high-efficiency particulate air filtering mask that can be cut to size. We carried out a randomised controlled cross-over study to compare the efficacy of such a mask (Totobobo, Dream Lab One Pte Ltd, Singapore) with fit-tested N95 masks (1860 or 1860s or 1862; 3M, St Paul, MN, USA) in 22 healthy volunteers. The median (interquartile range) reduction in airborne particle counts was significantly higher [193-fold (145–200)] for N95 masks than for Totobobo masks [135-fold (83–184)] (P < 0.05). There was no statistically significant difference between the proportion of subjects achieving a reduction of ≥100-fold between N95 (19/22) and Totobobo (16/22) masks. We conclude that use of the Totobobo mask without fit testing cannot be recommended, but its performance is sufficiently promising to warrant further investigation.
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Affiliation(s)
- S S W Au
- Department of Anaesthesia and Intensive Care, Chinese University of Hong Kong, Prince of Wales Hospital, Shatin, Hong Kong SAR, China
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17
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Eames I, Tang JW, Li Y, Wilson P. Airborne transmission of disease in hospitals. J R Soc Interface 2009; 6 Suppl 6:S697-702. [PMID: 19828499 DOI: 10.1098/rsif.2009.0407.focus] [Citation(s) in RCA: 95] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Hospital-acquired infection (HAI) is an important public health issue with unacceptable levels of morbidity and mortality, over the last 5 years. Disease can be transmitted by air (over large distances), by direct/indirect contact or a combination of both routes. While contact transmission of disease forms the majority of HAI cases, transmission through the air is harder to control, but one where the engineering sciences can play an important role in limiting the spread. This forms the focus of this themed volume. In this paper, we describe the current hospital environment and review the contributions from microbiologists, mechanical and civil engineers, and mathematicians to this themed volume on the airborne transmission of infection in hospitals. The review also points out some of the outstanding scientific questions and possible approaches to mitigating transmission.
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Affiliation(s)
- I Eames
- University College London, Gower Street, London WC1E 7JE, UK.
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18
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Humphreys H. Control and prevention of healthcare-associated tuberculosis: the role of respiratory isolation and personal respiratory protection. J Hosp Infect 2007; 66:1-5. [PMID: 17350724 DOI: 10.1016/j.jhin.2007.01.007] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2006] [Accepted: 01/18/2007] [Indexed: 11/27/2022]
Abstract
Although the prevalence of tuberculosis continues to decline in most developed countries, the risk of healthcare-associated tuberculosis, remains for patients or healthcare staff. Outbreaks of healthcare-associated tuberculosis are usually associated with delays in diagnosis and treatment, or the care of patients in sub-optimal facilities. The control and prevention of tuberculosis in hospitals is best achieved by three approaches, namely administrative (early investigation diagnosis, etc.), engineering (physical facilities e.g. ventilated isolation rooms) and personal respiratory protection (face sealing masks which are filtered). Recent guidelines on the prevention of tuberculosis in healthcare facilities from Europe and the USA have many common themes. In the UK, however, negative pressure isolation rooms are recommended only for patients with suspected multi-drug resistant TB and personal respiratory protection, i.e. filtered masks, are not considered necessary unless multi-drug resistant TB is suspected, or where aerosol-generating procedures are likely. In the US, the standard of care for patients with infectious tuberculosis is a negative pressure ventilated room and the use of personal respiratory protection for all healthcare workers entering the room of a patient with suspected or confirmed tuberculosis. The absence of clinical trials in this area precludes dogmatic recommendations. Nonetheless, observational studies and mathematical modelling suggest that all measures are required for effective prevention. Even when policies and facilities are optimal, there is a need to regularly review and audit these as sometimes compliance is less than optimal. The differences in recommendations may reflect the variations in epidemiology and the greater use of BCG vaccination in the UK compared with the United States. There is a strong argument for advising ventilated facilities and personal respiratory protection for the care of all patients with tuberculosis, as multi-drug tuberculosis may not always be apparent on admission, and these measures minimise transmission of all cases of TB to other patients and healthcare staff.
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Affiliation(s)
- H Humphreys
- Department of Clinical Microbiology, Royal College of Surgeons in Ireland and Beaumont Hospital, Dublin, Ireland.
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Schwartzman K. Tuberculosis Control in Developing and Developed Countries. Tuberculosis (Edinb) 2004. [DOI: 10.1007/978-3-642-18937-1_48] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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20
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Iwata K, Smith BA, Santos E, Polsky B, Sordillo EM. Failure to implement respiratory isolation: why does it happen? Infect Control Hosp Epidemiol 2002; 23:595-9. [PMID: 12400889 DOI: 10.1086/501977] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
BACKGROUND Respiratory isolation for 90% of individuals with acid-fast bacillus (AFB)-smear-positive tuberculosis (TB) is a recommended performance indicator in recent Infectious Diseases Society of America and Centers for Disease Control and Prevention guidelines. However, compliance with respiratory isolation reported from multiple centers in the United States and Europe falls short of that goal. OBJECTIVE To identify missed clues in TB patients who are not appropriately isolated. DESIGN Retrospective survey. SETTING A 900-bed voluntary hospital. PATIENTS All patients with AFB-smear-positive TB admitted between January 1995 and December 1999 who were not appropriately isolated. RESULTS There were 173 TB cases admitted, including 106 with pulmonary TB. AFB smears were positive in 82 cases; 24 (29%) of these were not appropriately isolated. During the study period, the number of TB cases declined, but the proportion of appropriately isolated patients did not change. Most isolation failure cases were men (median age, 45.5 years); 21 of these patients were black, 2 were Hispanic white, and 1 was Asian, but none was non-Hispanic white. All isolation failure cases had at least one characteristic predictive of TB that could have been elicited at admission (eg, abnormal chest radiograph findings consistent with TB, fever, weight loss, a history of TB, a positive result on tuberculin skin test, hemoptysis, and human immunodeficiency virus infection). CONCLUSION Consistent with experiences at other hospitals, we found that the rate of isolation failure remained unchanged despite an overall decline in TB cases. In our experience, almost all isolation failures could be avoided by careful review of the history, physical examination, and chest radiograph for characteristics classically considered predictive of TB.
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Affiliation(s)
- Kentaro Iwata
- Department of Medicine, St Luke's-Roosevelt Hospital Center, College of Physicians & Surgeons, Columbia University, New York, New York 10025, USA
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Starke JR. Transmission of mycobacterium tuberculosis to and from children and adolescents. ACTA ACUST UNITED AC 2001. [DOI: 10.1053/spid.2001.22785] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Abstract
Drug-resistant tuberculosis (TB) represents a threat to TB control programmes. Erratic and inappropriate use of currently available medications, HIV-TB co-infection, and concern about transmission of drug-resistant strains in the general population all contribute to a worrying picture. What do we do now? In the last few years, there has been considerable progress in the understanding of mechanisms of action and resistance to antituberculosis agents, and in establishing the value of directly observed therapy in preventing treatment failure. However, a limited effort has been devoted to the development of new active compounds or of rapid diagnostic tests, and their relevance to global tuberculosis control has been questioned.
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Affiliation(s)
- A Telenti
- Division of Infectious Diseases and Institute of Microbiology, Centre Hospitalier Universitaire Vaudois, Lausanne, Switzerland.
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