The impact of HIV on infectiousness of pulmonary tuberculosis: a community study in Zambia

The impact of a combined TB/HIV intervention on the incidence of TB infection among adolescents and young adults in the HPTN 071 (PopART) trial communities in Zambia and South Africa

BACKGROUND

HPTN071 (PopART) was a cluster randomized trial conducted in Zambian and South African (SA) communities, between 2013-2018. The PopART intervention (universal HIV-testing and treatment (UTT) combined with population-level TB symptom screening) was implemented in 14 communities. The TREATS study (2017-2021) was conducted to evaluate the impact of the PopART intervention on TB outcomes. We report on the impact of the combined TB/HIV intervention on the incidence of TB infection in a cohort of adolescents and young adults (AYA) aged 15-24 years.

METHODS

A random sample of AYA was enrolled between July 2018 and July 2019 in 7 intervention vs 7 standard-of-care communities. We collected questionnaire data on risk factors for TB, and blood for measuring TB infection using QuantiFERON (QFT) Plus. AYA were seen at months 12 and 24 with all procedures repeated. Primary outcome was incidence of TB infection comparing intervention and standard-of-care communities. An incident case was defined as a participant with QFT interferon-gamma response of < 0.2 IU/ml plasma ('negative') at baseline and a QFT interferon-gamma response of > = 0.7 IU/ml ('positive') at follow up.

RESULTS

We enrolled 4,648 AYA, 2,223 (47.8%) had a negative QFT-plus result at baseline, 1,902 (85.6%) had a follow up blood sample taken at 12 months or 24 months. Among the 1,902 AYA, followed for 2,987 person-years, 213 had incident TB infection giving (7.1 per 100 person-years). TB infection incidence rates were 8.7 per 100 person-years in intervention communities compared to 6.0 per 100 person-years in standard-of-care communities. There was no evidence the intervention reduced the transmission of TB (incidence-rate-ratio of 1.45, 95%CI 0.97-2.15, p = 0.063).

CONCLUSION

In our trial setting, we found no evidence that UTT combined with TB active case finding reduced the incidence of TB infection at population level. Our data will inform future modelling work to better understand the population level dynamics of HIV and TB.

Transmission Dynamics in Tuberculosis Patients with Human Immunodeficiency Virus: A Systematic Review and Meta-Analysis of 32 Observational Studies

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.

Advances in the understanding of Mycobacterium tuberculosis transmission in HIV-endemic settings

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.

Transmission of drug-resistant tuberculosis in HIV-endemic settings

The emergence and expansion of the multidrug-resistant tuberculosis epidemic is a threat to the global control of tuberculosis. Multidrug-resistant tuberculosis is the result of the selection of resistance-conferring mutations during inadequate antituberculosis treatment. However, HIV has a profound effect on the natural history of tuberculosis, manifesting in an increased rate of disease progression, leading to increased transmission and amplification of multidrug-resistant tuberculosis. Interventions specific to HIV-endemic areas are urgently needed to block tuberculosis transmission. These interventions should include a combination of rapid molecular diagnostics and improved chemotherapy to shorten the duration of infectiousness, implementation of infection control measures, and active screening of multidrug-resistant tuberculosis contacts, with prophylactic regimens for individuals without evidence of disease. Development and improvement of the efficacy of interventions will require a greater understanding of the factors affecting the transmission of multidrug-resistant tuberculosis in HIV-endemic settings, including population-based molecular epidemiology studies. In this Series article, we review what we know about the transmission of multidrug-resistant tuberculosis in settings with high burdens of HIV and define the research priorities required to develop more effective interventions, to diminish ongoing transmission and the amplification of drug resistance.

Does antiretroviral treatment increase the infectiousness of smear-positive pulmonary tuberculosis?

BACKGROUND

Understanding of the effects of human immunodeficiency virus (HIV) infection and antiretroviral treatment (ART) on Mycobacterium tuberculosis transmission dynamics remains limited. We undertook a cross-sectional study among household contacts of smear-positive pulmonary tuberculosis (TB) cases to assess the effect of established ART on the infectiousness of TB.

METHOD

Prevalence of tuberculin skin test (TST) positivity was compared between contacts of index cases aged 2-10 years who were HIV-negative, HIV-positive but not on ART, on ART for <1 year and on ART for 1 year. Random-effects logistic regression was used to take into account clustering within households.

RESULTS

Prevalence of M. tuberculosis infection in contacts of HIV-negative patients, HIV-positive patients on ART 1 year and HIV-positive patients not on ART/on ART <1 year index cases was respectively 44%, 21% and 22%. Compared to contacts of HIV-positive index cases not on ART or recently started on ART, the odds of TST positivity was similar in contacts of HIV-positive index cases on ART 1 year (adjusted OR [aOR] 1.0, 95%CI 0.3-3.7). The odds were 2.9 times higher in child contacts of HIV-negative index cases (aOR 2.9, 95%CI 1.0-8.2).

CONCLUSIONS

We found no evidence that established ART increased the infectiousness of smear-positive, HIV-positive index cases.

Risk factors for infectiousness of patients with tuberculosis: a systematic review and meta-analysis

We performed a systematic review and meta-analyses of studies assessing tuberculosis (TB) patient-related risk factors for transmission of Mycobacterium tuberculosis infection. Meta-analyses were conducted for sputum smear-positivity, lung cavitation and HIV seropositivity of index patients with both crude and adjusted odds ratios (AORs) pooled using random effect models. Thirty-seven studies were included in the review. We found that demographic characteristics such as age and sex were not significant risk factors, while behaviours such as smoking and alcohol intake were associated with infectiousness although inconsistently. Treatment delay of >28 days was a significant predictor of greater infectiousness. Contacts of sputum smear-positive index patients were found to be more likely to be infected than contacts of sputum smear-negative patients, with a pooled AOR of 2.15 (95% confidence interval (CI) 1.47-3.17, I 2 = 38%). Similarly, contacts of patients with the cavitary disease were around twice as likely to be infected as contacts of patients without cavitation (pooled AOR 1.9, 95% CI 1.26-2.84, I 2 = 63%). In contrast, HIV seropositive patients were associated with few contact infections than HIV seronegative patients (AOR 0.45, 95% CI 0.26-0.80, I 2 = 52%). In conclusion, behavioural and clinical characteristics of TB patients can be used to identify highly infectious patients for targeted interventions.

BUTIMBA: Intensifying the Hunt for Child TB in Swaziland through Household Contact Tracing

Background

Limited data exists to inform contact tracing guidelines in children and HIV-affected populations. We evaluated the yield and additionality of household contact and source case investigations in Swaziland, a TB/HIV high-burden setting, while prioritizing identification of childhood TB.

Methods

In partnership with 7 local TB clinics, we implemented standardized contact tracing of index cases (IC) receiving TB treatment. Prioritizing child contacts and HIV-affected households, screening officers screened contacts for TB symptoms and to identify risk factors associated with TB. We ascertained factors moderating the yield of contact tracing and measured the impact of our program by additional notifications.

Results

From March 2013 to November 2015, 3,258 ICs (54% bacteriologically confirmed; 70% HIV-infected; 85% adults) were enrolled leading to evaluation of 12,175 contacts (median age 18 years, IQR 24–42; 45% children; 9% HIV-infected). Among contacts, 196 TB cases (56% bacteriologically confirmed) were diagnosed resulting in a program yield of 1.6% for all forms of TB. The number needed to screen (NNS) to identify a bacteriologically confirmed TB case or all forms TB case traced from a child IC <5 years was respectively 62% and 40% greater than the NNS for tracing from an adult IC. In year one, we demonstrated a 32% increase in detection of bacteriologically confirmed child TB. Contacts were more likely to have TB if <5 years (OR = 2.0), HIV-infected (OR = 4.9), reporting ≥1 TB symptoms (OR = 7.7), and sharing a bed (OR = 1.7) or home (OR = 1.4) with the IC. There was a 1.4 fold increased chance of detecting a TB case in households known to be HIV-affected.

Conclusion

Contact tracing prioritizing children is not only feasible in a TB/HIV high-burden setting but contributes to overall case detection. Our findings support WHO guidelines prioritizing contact tracing among children and HIV-infected populations while highlighting potential to integrate TB and HIV case finding.

Diagnostic performance of smear microscopy and incremental yield of Xpert in detection of pulmonary tuberculosis in Rwanda

Background

Tuberculosis control program of Rwanda is currently phasing in light emitting diode-fluorescent microscopy (LED-FM) as an alternative to Ziehl-Neelsen (ZN) smear microscopy. This, alongside the newly introduced Xpert (Cepheid, Sunnyvale, CA, USA) is expected to improve diagnosis of tuberculosis and detection of rifampicin resistance in patients at health facilities. We assessed the accuracy of smear microscopy and the incremental sensitivity of Xpert at tuberculosis laboratories in Rwanda.

Methods

This was a cross-sectional study involving four laboratories performing ZN and four laboratories performing LED-FM microscopy. The laboratories include four intermediate (ILs) and four peripheral (PLs) laboratories. After smear microscopy, the left-over of samples, of a single early-morning sputum from 648 participants, were tested using Xpert and mycobacterial culture as a reference standard. Sensitivity of each test was compared and the incremental sensitivity of Xpert after a negative smear was assessed.

Results

A total of 96 presumptive pulmonary tuberculosis participants were culture positive for M. tuberculosis. The overall sensitivity in PL of ZN was 55.1 % (40.2–69.3 %), LED-FM was 37 % (19.4–57.6 %) and Xpert was 77.6 % (66.6–86.4 %) whereas in ILs the same value for ZN was 58.3 % (27.7–84.8 %), LED-FM was 62.5 % (24.5–91.5 %) and Xpert was 90 (68.3–98.8 %). The sensitivity for all tests was significantly higher among HIV-negative individuals (all test p <0.05). The overall incremental sensitivity of Xpert over smear microscopy was 32.3 %; p < 0.0001. The incremental sensitivity of Xpert was statistically significant for both smear methods at PL (32.9 %; p = 0.001) but not at the ILs (30 %; p = 0.125) for both smear methods.

Conclusions

Our study findings of the early implementation of the LED-FM did not reveal significant increment in sensitivity compared to the method being phased out (ZN). This study showed a significant incremental sensitivity for Xpert from both smear methods at peripheral centers where majority of TB patients are diagnosed. Overall our findings support the recommendation for Xpert as an initial diagnostic test in adults and children presumed to have TB.

Who Has Mycobacterial Disease? A Cross Sectional Study in Agropastoral Communities in Tanzania

Objective

To determine and describe clinical symptoms, demographic characteristics and environmental exposures as determinants of pulmonary mycobacterial diseases among patients examined for tuberculosis in agropastoral communities in Northern Tanzania.

Methods

This was a cross sectional study. Sputum samples were collected from patients attending three hospitals in Tanzania, and were investigated for pulmonary tuberculosis by microscopy between November 2010 and June 2012. The patients were interviewed about background information, and potential exposure to mycobacteria.

Results

We examined 1,711 presumptive tuberculosis cases where 936 (54.2%) were males and 775 (45.3%) females. Of all the study participants, 277 (16%) were found to have sputum samples positive for mycobacteria; 228 (13%) were smear positive, 123 (7%) were culture positive and 74 (4%) were positive by both smear microscopy and culture. Of the 123 mycobacterial culture positive, 15 (12.2%) had non-tuberculous mycobacteria. Males were more likely than females to be positive for mycobacteria. Factors associated with mycobacterial disease were loss of appetite, age groups below 41 years, and being a male. Among HIV negative patients, loss of appetite, age below 20 years and being a male were associated with being mycobacterial positive. Among HIV positive patients, males and those patients with a persistently coughing family member were more likely to harbor mycobacteria.

Conclusion

The findings in this study show that both M. tuberculosis and non-tuberculous mycobacterial strains were prevalent in the study community. Some risk factors were identified. Although the reported predictors may improve screening for mycobacterial diseases, their use requires some precaution.

Comparative meta-analysis of tuberculosis contact investigation interventions in eleven high burden countries

Background

Screening of household contacts of tuberculosis (TB) patients is a recommended strategy to improve early case detection. While it has been widely implemented in low prevalence countries, the most optimal protocols for contact investigation in high prevalence, low resource settings is yet to be determined. This study evaluated contact investigation interventions in eleven lower and middle income countries and reviewed the association between context or program-related factors and the yield of cases among contacts.

Methods

We reviewed data from nineteen first wave TB REACH funded projects piloting innovations to improve case detection. These nineteen had fulfilled the eligibility criteria: contact investigation implementation and complete data reporting. We performed a cross-sectional analysis of the percentage yield and case notifications for each project. Implementation strategies were delineated and the association between independent variables and yield was analyzed by fitting a random effects logistic regression.

Findings

Overall, the nineteen interventions screened 139,052 household contacts, showing great heterogeneity in the percentage yield of microscopy confirmed cases (SS+), ranging from 0.1% to 6.2%). Compared to the most restrictive testing criteria (at least two weeks of cough) the aOR’s for lesser (any TB related symptom) and least (all contacts) restrictive testing criteria were 1.71 (95%CI 0.94−3.13) and 6.90 (95% CI 3.42−13.93) respectively. The aOR for inclusion of SS- and extra-pulmonary TB was 0.31 (95% CI 0.15−0.62) compared to restricting index cases to SS+ TB. Contact investigation contributed between <1% and 14% to all SS+ cases diagnosed in the intervention areas.

Conclusions

This study confirms that high numbers of active TB cases can be identified through contact investigation in a variety of contexts. However, design and program implementation factors appear to influence the yield of contact investigation and its concomitant contribution to TB case detection.

Clinical Aspects of Adult Tuberculosis

Tuberculosis (TB) in adults can present in a large number of ways. The lung is the predominant site of TB. Primary pulmonary TB should be distinguished from postprimary pulmonary TB, which is the most frequent TB manifestation in adults (70%-80% cases). Cough is common, although the chest radiograph often raises suspicion of disease. Sputum sampling is a key step in the diagnosis of TB, and invasive procedures such as bronchoscopy may be necessary to achieve adequate samples for diagnosis. Extrapulmonary involvement, which may present many years after exposure, occurs in a variable proportion of cases (20%-45%). This reflects the country of origin of patients and also the frequency of associated human immunodeficiency virus (HIV) coinfection. In the latter case, the presentation of TB is often nonspecific, and care needs to be taken to not miss the diagnosis. Anti-TB therapy should be given in line with proven (or assumed) drug resistance. In extrapulmonary TB, adjunctive therapeutic measures may be indicated; although in all cases, support is often required to ensure that people are able to complete treatment with minimal adverse events and maximal adherence to the prescribed regimen, and so reduce risk of future disease for themselves and others.

Impact of co-infections and BCG immunisation on immune responses among household contacts of tuberculosis patients in a Ugandan cohort

BACKGROUND

Tuberculosis incidence in resource poor countries remains high. We hypothesized that immune modulating co-infections such as helminths, malaria, and HIV increase susceptibility to latent tuberculosis infection (LTBI), thereby contributing to maintaining the tuberculosis epidemic.

METHODS

Adults with sputum-positive tuberculosis (index cases) and their eligible household contacts (HHCs) were recruited to a cohort study between May 2011 and January 2012. HHCs were investigated for helminths, malaria, and HIV at enrolment. HHCs were tested using the QuantiFERON-TB Gold In-Tube (QFN) assay at enrolment and six months later. Overnight whole blood culture supernatants from baseline QFN assays were analyzed for cytokine responses using an 11-plex Luminex assay. Associations between outcomes (LTBI or cytokine responses) and exposures (co-infections and other risk factors) were examined using multivariable logistic and linear regression models.

RESULTS

We enrolled 101 index cases and 291 HHCs. Among HHCs, baseline prevalence of helminths was 9% (25/291), malaria 16% (47/291), HIV 6% (16/291), and LTBI 65% (179/277). Adjusting for other risk factors and household clustering, there was no association between LTBI and any co-infection at baseline or at six months: adjusted odds ratio (95% confidence interval (CI); p-value) at baseline for any helminth, 1.01 (0.39-2.66; 0.96); hookworm, 2.81 (0.56-14.14; 0.20); malaria, 1.06 (0.48-2.35; 0.87); HIV, 0.74 (0.22-2.47; 0.63). HHCs with LTBI had elevated cytokine responses to tuberculosis antigens but co-infections had little effect on cytokine responses. Exploring other risk factors, Th1 cytokines among LTBI-positive HHCs with BCG scars were greatly reduced compared to those without scars: (adjusted geometric mean ratio) IFNγ 0.20 (0.09-0.42), <0.0001; IL-2 0.34 (0.20-0.59), <0.0001; and TNFα 0.36 (0.16-0.79), 0.01.

CONCLUSIONS

We found no evidence that co-infections increase the risk of LTBI, or influence the cytokine response profile among those with LTBI. Prior BCG exposure may reduce Th1 cytokine responses in LTBI.

X ray screening at entry and systematic screening for the control of tuberculosis in a highly endemic prison

BACKGROUND

Tuberculosis (TB) is a major issue in prisons of low and middle income countries where TB incidence rates are much higher in prison populations as compared with the general population. In the Rio de Janeiro (RJ) State prison system, the TB control program is limited to passive case-finding and supervised short duration treatment. The aim of this study was to measure the impact of X-ray screening at entry associated with systematic screening on the prevalence and incidence of active TB.

METHODS

We followed up for 2 years a RJ State prison for adult males (1429 inmates at the beginning of the study) and performed, in addition to passive case-finding, 1) two "cross-sectional" X-ray systematic screenings: the first at the beginning of the study period and the second 13 months later; 2) X-ray screening of inmates entering the prison during the 2 year study period. Bacteriological examinations were performed in inmates presenting any pulmonary, pleural or mediastinal X-ray abnormality or spontaneously attending the prison clinic for symptoms suggestive of TB.

RESULTS

Overall, 4326 X-rays were performed and 246 TB cases were identified. Prevalence among entering inmates remained similar during 1st and the 2nd year of the study: 2.8% (21/754) and 2.9% (28/954) respectively, whereas prevalence decreased from 6.0% (83/1374) to 2.8% (35/1244) between 1st and 2nd systematic screenings (p < 0.0001). Incidence rates of cases identified by passive case-finding decreased from 42 to 19 per 1000 person-years between the 1st and the 2nd year (p < 0.0001). Cases identified by screenings were less likely to be bacteriologically confirmed as compared with cases identified by passive-case finding.

CONCLUSIONS

The strategy investigated, which seems highly effective, should be considered in highly endemic confined settings such as prisons.

Contact investigation for tuberculosis: a systematic review and meta-analysis

Investigation of contacts of patients with tuberculosis (TB) is a priority for TB control in high-income countries, and is increasingly being considered in resource-limited settings. This review was commissioned for a World Health Organization Expert Panel to develop global contact investigation guidelines. We performed a systematic review and meta-analysis of all studies reporting the prevalence of TB and latent TB infection, and the annual incidence of TB among contacts of patients with TB. After screening 9,555 titles, we included 203 published studies. In 95 studies from low- and middle-income settings, the prevalence of active TB in all contacts was 3.1% (95% CI 2.2-4.4%, I(2)=99.4%), microbiologically proven TB was 1.2% (95% CI 0.9-1.8%, I(2)=95.9%), and latent TB infection was 51.5% (95% CI 47.1-55.8%, I(2)=98.9%). The prevalence of TB among household contacts was 3.1% (95% CI 2.1-4.5%, I(2)=98.8%) and among contacts of patients with multidrug-resistant or extensively drug-resistant TB was 3.4% (95% CI 0.8-12.6%, I(2)=95.7%). Incidence was greatest in the first year after exposure. In 108 studies from high-income settings, the prevalence of TB among contacts was 1.4% (95% CI 1.1-1.8%, I(2)=98.7%), and the prevalence of latent infection was 28.1% (95% CI 24.2-32.4%, I(2)=99.5%). There was substantial heterogeneity among published studies. Contacts of TB patients are a high-risk group for developing TB, particularly within the first year. Children <5 yrs of age and people living with HIV are particularly at risk. Policy recommendations must consider evidence of the cost-effectiveness of various contact tracing strategies, and also incorporate complementary strategies to enhance case finding.

Modeling the dynamic relationship between HIV and the risk of drug-resistant tuberculosis

The emergence of highly drug-resistant tuberculosis (TB) and interactions between TB and HIV epidemics pose serious challenges for TB control. Previous researchers have presented several hypotheses for why HIV-coinfected TB patients may suffer an increased risk of drug-resistant TB (DRTB) compared to other TB patients. Although some studies have found a positive association between an individual's HIV status and his or her subsequent risk of multidrug-resistant TB (MDRTB), the observed individual-level relationship between HIV and DRTB varies substantially among settings. Here, we develop a modeling framework to explore the effect of HIV on the dynamics of DRTB. The model captures the acquisition of resistance to important classes of TB drugs, imposes fitness costs associated with resistance-conferring mutations, and allows for subsequent restoration of fitness because of compensatory mutations. Despite uncertainty in several key parameters, we demonstrate epidemic behavior that is robust over a range of assumptions. Whereas HIV facilitates the emergence of MDRTB within a community over several decades, HIV-seropositive individuals presenting with TB may, counterintuitively, be at lower risk of drug-resistant TB at early stages of the co-epidemic. This situation arises because many individuals with incident HIV infection will already harbor latent Mycobacterium tuberculosis infection acquired at an earlier time when drug resistance was less prevalent. We find that the rise of HIV can increase the prevalence of MDRTB within populations even as it lowers the average fitness of circulating MDRTB strains compared to similar populations unaffected by HIV. Preferential social mixing among individuals with similar HIV status and lower average CD4 counts among HIV-seropositive individuals further increase the expected burden of MDRTB. This model suggests that the individual-level association between HIV and drug-resistant forms of TB is dynamic, and therefore, cross-sectional studies that do not report a positive individual-level association will not provide assurance that HIV does not exacerbate the burden of resistant TB in the community.

Monitoring CD27 expression to evaluate Mycobacterium tuberculosis activity in HIV-1 infected individuals in vivo

The level of bacterial activity is only poorly defined during asymptomatic Mycobacterium tuberculosis (MTB) infection. The objective was to study the capacity of a new biomarker, the expression of the T cell maturation marker CD27 on MTB-specific CD4 T cells, to identify active tuberculosis (TB) disease in subjects from a MTB and HIV endemic region. The frequency and CD27 expression of circulating MTB-specific CD4 T cells was determined in 96 study participants after stimulation with purified protein derivative (PPD) using intracellular cytokine staining for IFNgamma (IFNγ). Subjects were then stratified by their TB and HIV status. Within PPD responders, a CD27⁻ phenotype was associated with active TB in HIV⁻ (p = 0.0003) and HIV⁺ (p = 0.057) subjects, respectively. In addition, loss of CD27 expression preceded development of active TB in one HIV seroconverter. Interestingly, in contrast to HIV⁻ subjects, MTB-specific CD4 T cell populations from HIV⁺ TB-asymptomatic subjects were often dominated by CD27⁻ cells. These data indicate that down-regulation of CD27 on MTB-specific CD4 T cell could be used as a biomarker of active TB, potentially preceding clinical TB disease. Furthermore, these data are consistent with the hypothesis that late, chronic HIV infection is frequently associated with increased mycobacterial activity in vivo. The analysis of T cell maturation and activation markers might thus be a useful tool to monitor TB disease progression.

High prevalence of pulmonary tuberculosis and inadequate case finding in rural western Kenya

RATIONALE

Limited information exists on the prevalence of tuberculosis and adequacy of case finding in African populations with high rates of HIV.

OBJECTIVES

To estimate the prevalence of bacteriologically confirmed pulmonary tuberculosis (PTB) and the fraction attributable to HIV, and to evaluate case detection.

METHODS

Residents aged 15 years and older, from 40 randomly sampled clusters, provided two sputum samples for microscopy; those with chest radiograph abnormalities or symptoms suggestive of PTB provided one additional sputum sample for culture.

MEASUREMENTS AND MAIN RESULTS

PTB was defined by a culture positive for Mycobacterium tuberculosis or two positive smears. Persons with PTB were offered HIV testing and interviewed on care-seeking behavior. We estimated the population-attributable fraction of HIV on prevalent and notified PTB, the patient diagnostic rate, and case detection rate using provincial TB notification data. Among 20,566 participants, 123 had PTB. TB prevalence was 6.0/1,000 (95% confidence interval, 4.6-7.4) for all PTB and 2.5/1,000 (1.6-3.4) for smear-positive PTB. Of 101 prevalent TB cases tested, 52 (51%) were HIV infected, and 58 (64%) of 91 cases who were not on treatment and were interviewed had not sought care. Forty-eight percent of prevalent and 65% of notified PTB cases were attributable to HIV. For smear-positive and smear-negative PTB combined, the patient diagnostic rate was 1.4 cases detected per person-year among HIV-infected persons having PTB and 0.6 for those who were HIV uninfected, corresponding to case detection rates of 56 and 65%, respectively.

CONCLUSIONS

Undiagnosed PTB is common in this community. TB case finding needs improvement, for instance through intensified case finding with mobile smear microscopy services, rigorous HIV testing, and improved diagnosis of smear-negative TB.

Quality of tuberculosis care and its association with patient adherence to treatment in eight Ethiopian districts

BACKGROUND

Little is known about the quality of tuberculosis (TB) service delivery in public health facilities in Ethiopia and its association with patients' non-adherence to TB treatment. This study assessed the organization, management and processes of TB care delivery, and their effects on patients' adherence to TB treatment.

METHODS

The quality of TB care was investigated in 44 public health facilities from three perspectives: structure, processes of TB care delivery and patient treatment outcome. Quality of care was determined by adherence to national TB guidelines. On-site observations of TB service delivery and interviews with health providers were conducted to evaluate structural factors. Patients (n = 237) in the health facilities were interviewed prospectively at completion of their treatment to determine the quality of tuberculosis care delivered. Three measures of treatment adherence [treatment interruption (>or=2 weeks), availability of unused TB drugs and treatment default] were quantified from a review of patient treatment registers and an audit of unused TB drugs at patients' homes. Effects were identified of poor quality structures and processes of service delivery on these three measures of adherence.

RESULTS

TB care providers were untrained in 18 (44%) of 44 facilities and daily outpatient TB care was not given in 13 of 44 (25%). Among the 237 patients, 43% interrupted treatment for >or=15 days and 30% had at least 1 day's dose of TB drugs unused. Patients tended to interrupt and default from treatment when their care provider had been inadequately supervised by district TB control experts and was incapable of dealing with patients' minor illnesses. Unavailability of daily TB care in health facilities was associated with missing daily doses.

CONCLUSION

Better training of TB care providers and district supervisory support could be important interventions to improve the quality of care delivery and patient adherence to treatment.

Prevalence of tuberculosis, HIV and respiratory symptoms in two Zambian communities: implications for tuberculosis control in the era of HIV

BACKGROUND

The Stop TB Partnership target for tuberculosis is to have reduced the prevalence of tuberculosis by 50% comparing 2015 to 1990. This target is challenging as few prevalence surveys have been conducted, especially in high burden tuberculosis and HIV countries. Current tuberculosis control strategies in high HIV prevalent settings are therefore based on limited epidemiological evidence and more evidence is needed from community-based surveys to inform improved policy formulation.

METHODS AND FINDINGS

8044 adults were sampled from 2 sub-districts (wards) in Lusaka province, Zambia. Questionnaires were used to screen for symptoms, respiratory samples were obtained for culture and oral secretions collected for HIV testing. 79 individuals were found to have Mycobacterium tuberculosis in their sputum, giving an adjusted overall prevalence of tuberculosis of 870/100,000 (95% CI 570-1160/100,000). The adjusted overall prevalence of HIV was 28.61% (95% CI 26.04-31.19). HIV- infection was significantly associated with prevalent tuberculosis (Adj OR 2.3, 95% CI 1.42-3.74) and the population attributable fraction of HIV for prevalent tuberculosis was 36%. Symptoms such as prolonged cough (adj OR 12.72, 95% CI 7.05-22.94) and fever (Adj OR 2.04, 95%CI 1.23-3.39), were associated with prevalent tuberculosis, but 8 (10%) individuals with prevalent tuberculosis denied having any symptoms at all and only 34 (43%) would have been classified as a TB suspect by current guidelines.

CONCLUSIONS

Undiagnosed tuberculosis is a challenge for tuberculosis control and new approaches are needed if we are to reach international targets. Epidemiological studies can inform screening algorithms for both detection and prevention of active tuberculosis.

The detection of airborne transmission of tuberculosis from HIV-infected patients, using an in vivo air sampling model

BACKGROUND

Nosocomial transmission of tuberculosis remains an important public health problem. We created an in vivo air sampling model to study airborne transmission of tuberculosis from patients coinfected with human immunodeficiency virus (HIV) and to evaluate environmental control measures.

METHODS

An animal facility was built above a mechanically ventilated HIV-tuberculosis ward in Lima, Peru. A mean of 92 guinea pigs were continuously exposed to all ward exhaust air for 16 months. Animals had tuberculin skin tests performed at monthly intervals, and those with positive reactions were removed for autopsy and culture for tuberculosis.

RESULTS

Over 505 consecutive days, there were 118 ward admissions by 97 patients with pulmonary tuberculosis, with a median duration of hospitalization of 11 days. All patients were infected with HIV and constituted a heterogeneous group with both new and existing diagnoses of tuberculosis. There was a wide variation in monthly rates of guinea pigs developing positive tuberculin test results (0%-53%). Of 292 animals exposed to ward air, 159 developed positive tuberculin skin test results, of which 129 had laboratory confirmation of tuberculosis. The HIV-positive patients with pulmonary tuberculosis produced a mean of 8.2 infectious quanta per hour, compared with 1.25 for HIV-negative patients with tuberculosis in similar studies from the 1950s. The mean monthly patient infectiousness varied greatly, from production of 0-44 infectious quanta per hour, as did the theoretical risk for a health care worker to acquire tuberculosis by breathing ward air.

CONCLUSIONS

HIV-positive patients with tuberculosis varied greatly in their infectiousness, and some were highly infectious. Use of environmental control strategies for nosocomial tuberculosis is therefore a priority, especially in areas with a high prevalence of both tuberculosis and HIV infection.

Factors influencing sputum smear and culture conversion time among patients with new case pulmonary tuberculosis

Sputum smear and culture conversion are important indicators for the effectiveness of treatment and the infectivity of the patient. The aim of this study was to identify the factors influencing both sputum smear and culture conversion time among patients with new case pulmonary tuberculosis (TB). The study was conducted in a reference hospital in Turkey in which 737 patients with pulmonary TB were hospitalised between January 2000 and 2005. We evaluated 306 (193 men and 113 women) human immunodeficiency virus-negative patients diagnosed with new case pulmonary TB. Factors associated with both sputum smear and culture conversion time (days) were investigated. Patients with diabetes mellitus (DM), cavitary disease, radiologically extensive disease had longer sputum smear and culture conversion time than the other groups. In addition, old age, male sex, smoking and thrombocytosis were found to be significantly associated with sputum smear conversion time. In the logistic regression analysis, the presence of DM and extensive disease were determined as independent factors associated with persistent sputum smear and culture positivity at the end of 2 months. The presence of DM and extensive disease were found to be independent risk factors influencing both sputum smear and culture conversion time in pulmonary TB. Sputum smear and culture examinations should be considered together to assess the poor prognosis.

A case for passive immunoprophylaxis against tuberculosis

HIV-associated tuberculosis is escalating ominously in Africa and southeast Asia despite existing control measures. Therefore, new approaches to tuberculosis control need to be explored. We discuss the potential use of passive immunoprophylaxis with antibodies in tuberculosis control. Although the predominant type of active host resistance is T-cell mediated, recent results in mouse experimental models suggest that monoclonal antibodies to certain antigens (eg, Acr or lipoarabinomannan) can impart substantial passive protection against tuberculous infection. These results are corroborated by data from other laboratories on passive vaccination against a number of intracellular microbial pathogens. Further work is needed to develop human (or humanised) antibody reagents, to increase their protective efficacy, and to expand our understanding of the mechanisms of antibody action.

Tuberculosis transmission attributable to close contacts and HIV status, Malawi

In this population, ≈90% of M. tuberculosis infections were transmitted by casual contact, and nearly half from HIV-positive patients.

We conducted the first molecular study of tuberculosis (TB) to estimate the role of household contact and transmission from HIV-positive putative source contacts (PSCs) in a high HIV-prevalence area. TB patients in a long-term population-based study in Malawi were asked about past contact with TB. DNA fingerprinting was used to define clusters of cases with identical strains. Among 143 epidemiologically defined PSC-case pairs, fingerprinting confirmed transmission for 44% of household and family contacts and 18% of other contacts. Transmission was less likely to be confirmed if the PSC were HIV positive than if he or she was HIV negative (odds ratio 0.32, 95% confidence interval [CI] 0.14–0.74). Overall, epidemiologic links were found for 11% of 754 fingerprint-clustered cases. We estimate that 9%–13% of TB cases were attributable to recent transmission from identifiable close contacts and that nearly half of the TB cases arising from recent infection had acquired the infection from HIV-positive patients.

Undiagnosed tuberculosis in a community with high HIV prevalence: implications for tuberculosis control

BACKGROUND

Although failure of tuberculosis (TB) control in sub-Saharan Africa is attributed to the HIV epidemic, it is unclear why the directly observed therapy short-course (DOTS) strategy is insufficient in this setting. We conducted a cross-sectional survey of pulmonary TB (PTB) and HIV infection in a community of 13,000 with high HIV prevalence and high TB notification rate and a well-functioning DOTS TB control program.

METHODS

Active case finding for PTB was performed in 762 adults using sputum microscopy and Mycobacterium tuberculosis culture, testing for HIV, and a symptom and risk factor questionnaire. Survey findings were correlated with notification data extracted from the TB treatment register.

RESULTS

Of those surveyed, 174 (23%) tested HIV positive, 11 (7 HIV positive) were receiving TB therapy, 6 (5 HIV positive) had previously undiagnosed smear-positive PTB, and 6 (4 HIV positive) had smear-negative/culture-positive PTB. Symptoms were not a useful screen for PTB. Among HIV-positive and -negative individuals, prevalence of notified smear-positive PTB was 1,563/100,000 and 352/100,000, undiagnosed smear-positive PTB prevalence was 2,837/100,000 and 175/100,000, and case-finding proportions were 37 and 67%, respectively. Estimated duration of infectiousness was similar for HIV-positive and HIV-negative individuals. However, 87% of total person-years of undiagnosed smear-positive TB in the community were among HIV-infected individuals.

CONCLUSIONS

PTB was identified in 9% of HIV-infected individuals, with 5% being previously undiagnosed. Lack of symptoms suggestive of PTB may contribute to low case-finding rates. DOTS strategy based on passive case finding should be supplemented by active case finding targeting HIV-infected individuals.

Towards universal access to HIV prevention, treatment, care, and support: the role of tuberculosis/HIV collaboration

Tuberculosis is the oldest of the world's current pandemics and causes 8.9 million new cases and 1.7 million deaths annually. The disease is among the most common causes of morbidity and mortality in people living with HIV. However, tuberculosis is more than just part of the global HIV problem; well-resourced tuberculosis programmes are an important part of the solution to scaling-up towards universal access to comprehensive HIV prevention, diagnosis, care, and support. This article reviews the impact of the interactions between tuberculosis and HIV in resource-limited settings; outlines the recommended programmatic and clinical responses to the dual epidemics, highlighting the role of tuberculosis/HIV collaboration in increasing access to prevention, diagnostic, and treatment services; and reviews progress in the global response to the epidemic of HIV-related tuberculosis.

The impact of the HIV epidemic on tuberculosis transmission in Tanzania

OBJECTIVE

To assess the impact of the HIV epidemic on tuberculosis transmission in Tanzania by estimating the trend in annual risk of tuberculosis infection (ARTI) over the period 1983-2003.

DESIGN

Tuberculin survey among school children aged 6-14 years, randomly selected by cluster sampling.

METHODS

Primary outcome was the ARTI among children without a BCG vaccination scar. To obtain time trends, data were reanalysed from three previous surveys carried out at intervals of 5 years since 1983, using identical methods and definitions.

RESULTS

Of 96,226 children included in the analysis (74% of those enrolled), 10,239 (11%) had no BCG scar. The ARTI was 0.68% (95% confidence interval 0.55-0.81). Despite a doubling of notification rates of smear-positive tuberculosis since 1983, this represents an average annual decline since the first survey of 2.7% (P < 0.001). The declining trend in ARTI was observed in 17 of 20 regions, with no association between this trend and region-specific prevalence of HIV infection among patients with tuberculosis (P = 0.575). A similar decline in ARTI was observed among children with a BCG scar and for various ways of estimating the prevalence of tuberculosis infection from the distribution of skin test reactions.

CONCLUSION

Despite substantial increases in tuberculosis incidence, the overall population-level effect of the HIV epidemic on tuberculosis transmission in Tanzania has been limited. This suggests that in the presence of a strong control programme, the HIV epidemic has limited impact on tuberculosis transmission.

Number of negative acid-fast smears needed to adequately assess infectivity of patients with pulmonary tuberculosis

STUDY OBJECTIVES

To investigate the relationship between the number of negative acid-fast bacilli (AFB) smear results and infectivity of pulmonary tuberculosis (TB).

DESIGN

Retrospective analysis.

METHODS AND SUBJECTS

We examined 122 index cases in Harris County, TX, reported in 1998 and 1999. All cases had only negative AFB smear results during the infectious period and were categorized in two groups: group A consisted of cases with only one or two sputum specimens collected and processed, and group B consisted of cases with at least three sputum specimens or at least one bronchoscopic specimen. Tuberculin skin test (TST) results of contacts were ascertained from the results of contact investigations performed by the City of Houston Department of Health and Human Services, Tuberculosis Control Division. Univariate and multivariate analyses were done to explore index case and contact attributes associated with tuberculosis (TB) transmission using positive TST results of contacts as a measure of recent transmission.

RESULTS

We found male gender and younger age of index cases along with Hispanic ethnicity of contacts to be independently associated with positive TST results, while younger contacts were less likely to be TST positive. Smear category of the index case (group A vs group B) was not independently associated with transmission. We also found that the first two sputum specimens in cases where three or more were performed yielded 90% of all positive culture results for Mycobacterium tuberculosis (MTB).

CONCLUSIONS

We conclude that two sputum specimens negative for AFB stain are adequate for both assessing infectivity and for isolating MTB from patients with pulmonary TB.

The impact of HIV/AIDS on the control of tuberculosis in India

Epidemics of HIV/AIDS have increased the tuberculosis (TB) case-load by five or more times in East Africa and southern Africa. As HIV continues to spread, warnings have been issued of disastrous AIDS and TB epidemics in "new-wave" countries, including India, which accounts for 20% of all new TB cases arising in the world each year. Here we investigate whether, in the face of the HIV epidemic, India's Revised National TB Control Program (RNTCP) could halve TB prevalence and death rates in the period 1990-2015, as specified by the United Nations Millennium Development Goals. Using a mathematical model to capture the spatial and temporal variation in TB and HIV in India, we predict that, without the RNTCP, HIV would increase TB prevalence (by 1%), incidence (by 12%), and mortality rates (by 33%) between 1990 and 2015. With the RNTCP, however, we expect substantial reductions in prevalence (by 68%), incidence (by 41%), and mortality (by 39%) between 1990 and 2015. In India, 29% of adults but 72% of HIV-positive adults live in four large states in the south where, even with the RNTCP, mortality is expected to fall by only 15% between 1990 and 2015. Nationally, the RNTCP should be able to reverse the increases in TB burden due to HIV but, to ensure that TB mortality is reduced by 50% or more by 2015, HIV-infected TB patients should be provided with antiretroviral therapy in addition to the recommended treatment for TB.

Tuberculosis in household contacts of infectious cases in Kampala, Uganda

Tuberculosis remains a serious threat to public health, especially in sub-Saharan Africa. To determine the host and environmental factors responsible for tuberculosis in African households, the authors performed a prospective cohort study of 1,206 household contacts of 302 index cases with tuberculosis enrolled in Uganda between 1995 and 1999. All contacts were systematically evaluated for active tuberculosis and risk factors for active disease. Among the 1,206 household contacts, 76 secondary cases (6%) of tuberculosis were identified. Of these cases, 51 were identified in the baseline evaluation, and 25 developed during follow-up. Compared with index cases, secondary cases presented more often with minimal disease. The risk for secondary tuberculosis was greater among young children than adults (10% vs. 1.9%) and among human immunodeficiency virus-seropositive than -seronegative contacts (23% vs. 3.3%). Host risk factors could not be completely separated from the effects of environmental risk factors, suggesting that a household may represent a complex system of interacting risks for tuberculosis.

Can we control tuberculosis in high HIV prevalence settings?

The overlap between the epidemiology of HIV and tuberculosis and consequent rapid rise in numbers of patients with tuberculosis in many African countries has put a huge burden on health systems. The stigma of HIV has increased the existing stigma surrounding tuberculosis. There are three mechanisms by which we may reduce the number of cases of tuberculosis in a community: reducing transmission of tuberculosis, reducing reactivation of latent tuberculosis infection and reducing HIV transmission. Reinforcing the existing health service to find more cases, active case-finding in communities or enhanced case-finding in specific groups will reduce transmission of tuberculosis. However, health services that find it difficult to find cases efficiently will also find it difficult to support patients throughout treatment to achieve a cure. Partnership with traditional healers, community-based organizations and private practitioners could reduce this burden. Reactivation of tuberculosis among people living with HIV can be reduced by tuberculosis preventive therapy or by antiretroviral therapy. Programmes that identify people living with HIV can also implement enhanced tuberculosis case-finding increasing the benefits of the programme. However, the impact of widespread use of antiretroviral therapy may be to increase the number of people in a community who are mildly immunocompromised and the incidence of tuberculosis at a community level might rise. Any strategy that successfully reduces HIV transmission will benefit tuberculosis control, since around a third of all HIV-positive individuals will develop tuberculosis before they die. To control tuberculosis in high HIV prevalence settings, we must strengthen health systems to include not only expansion of the DOTS strategy but also full-blooded implementation of voluntary counselling and testing, enhanced and active tuberculosis case-finding, preventive therapy and better care for people living with HIV including antiretroviral therapy. The approach needed to control tuberculosis needs also to be integrated into broader development and poverty reduction goals.

Survival of patients with pulmonary tuberculosis: clinical and molecular epidemiologic factors

Using restriction fragment-length polymorphism data, we conducted a retrospective cohort study of 139 adult patients with pulmonary tuberculosis to investigate the clinical impact of Mycobacterium tuberculosis infection with a clustered isolate. The cumulative all-cause mortality rate during treatment was 21%. Patients with clustered DNA fingerprint patterns had a reduced risk of death, compared with patients with unique patterns (hazard ratio [HR], 0.5; 95% confidence interval [CI], 0.2-1.1), but this finding was confounded by age (adjusted HR, 0.8; 95% CI, 0.4-1.8). After adjustment for age, the strongest predictors of death were such underlying illnesses as diabetes mellitus, renal failure, chronic obstructive pulmonary disease, and human immunodeficiency virus infection. We conclude that comorbidity and immunosuppression are important predictors of survival for patients with pulmonary tuberculosis in an inner-city cohort. Recently transmitted infection, as determined by use of DNA fingerprinting to classify patients' isolates as being either clustered or unique, was not independently associated with death.

The global tuberculosis situation. Progress and problems in the 20th century, prospects for the 21st century

Mycobacterium tuberculosis has been identified in prehistoric remains of humans. Despite references to TB by Hippocrates and Galen, humankind had limited understanding of and few tools to defend itself against TB until the later 19th century. Subsequently, landmark advances in the 20th century provided the means to control and prevent this disease. At the same time, epidemiological developments and fundamental problems related to human behavior, socioeconomic conditions, and political circumstances continue to thwart efforts to diminish the burden of suffering and death caused by TB. This article reviewed some of these issues including the global failure of TB control in the late 20th century, the worldwide emergence of drug-resistant TB, the extensive spread of HIV infection and its impact on TB incidence; and changing health care and political environments. The obstacles to TB control remain and will remain challenges in the coming years. Still, recent developments in immunology, biochemistry, and molecular biology suggest that new knowledge and tools are just around the corner. These will enhance the ability to conquer this microbe by the end of the current century.

Clinical features of tuberculosis among adults in sub-Saharan Africa in the 21st century

Although tuberculosis was unknown in sub-Saharan Africa before the 19th century, rapid spread of infections due to Mycobacterium tuberculosis occurred during the 20th century and could be found in up to 50% of the adult population by the 1950s. Owing to changes in age structure, rapid urbanization associated with overcrowding living conditions, increasing poverty and the HIV epidemic a 300-400% increase in tuberculosis cases and deaths has been reported from sub-Saharan Africa. Persons dually infected with HIV and tuberculosis may have active tuberculosis with typical or atypical clinical features and/or involving multiple organ systems. In addition, mycobacteraemia associated with non-specific clinical features is common among HIV-infected persons, especially if they are severely immunocompromised. Because of the atypical clinical features these patients are easily misdiagnosed and are therefore likely to die from what is otherwise a curable illness. Consequently there is a need to better characterize the clinical features of all forms of tuberculosis, especially in the presence of HIV infection.

Transmission of Mycobacterium tuberculosis to contacts of HIV-infected tuberculosis patients

We assessed the infectiousness of human immunodeficiency virus (HIV)-seropositive and HIV-seronegative individuals with pulmonary tuberculosis (TB) in a prospective cohort study. We enrolled, evaluated, and followed 104 close contacts of HIV-seropositive pulmonary TB patients and 256 close contacts of HIV-seronegative pulmonary TB patients using a standardized questionnaire, symptom review, chest radiograph, HIV serology, and tuberculin skin testing (TST). Contacts were followed for > or = 12 mo. TB infection at enrollment was 27% (28/104) among contacts of HIV-seropositive TB patients and 35% (90/256) among contacts of HIV-seronegative TB patients (odds ratio [OR] = 0.68, 95% confidence interval [CI] 0.41 to 1.12; p = 0.130). TST conversion occurred in 21% (42/ 204) of subjects; 8% (5/63) of contacts of HIV-seropositive index cases and 26% (37/141) of contacts of HIV-seronegative index cases (OR = 0.24, 95% CI 0.09 to 0.65; p = 0.003). TB was diagnosed in nine contacts; eight were contacts of HIV-seronegative index cases. HIV seropositivity in the index case was independently associated with a lower risk of TB infection among contacts, even among household contacts younger than 15 yr of age. Contacts of HIV-seropositive persons with pulmonary TB were less likely to have a positive TST response at 1 yr of follow-up than contacts of HIV-seronegative persons.

The impact of human immunodeficiency virus type 1 on infectiousness of tuberculosis: a meta-analysis

To assess if the relative infectiousness of patients with tuberculosis is enhanced by coinfection with human immunodeficiency virus type 1 (HIV-1), data from 6 studies of 1240 health care workers who had contact with tuberculosis patients were analyzed. Overall rates of tuberculin skin test conversion were similar regardless of HIV-1 positivity of tuberculosis patients (odds ratio [OR], 1.04; 95% confidence interval [CI], 0.23-1.84). However, when only 3 studies during nosocomial outbreaks of multidrug-resistant Mycobacterium tuberculosis were analyzed, rates of skin test conversion were higher among contacts of HIV-1-positive index cases (OR, 2.85; 95% CI, 1.85-3.85; P=.0002). A second meta-analysis included data from 11 studies of 10,714 household contacts of tuberculosis patients. Prevalence of both skin test positivity (OR, 0.45; 95% CI, 0.20-1.03) and active disease (OR, 1.17; 95% CI, 0.78-1.56) were similar regardless of HIV-1 positivity of index cases. These data suggest that tuberculosis patients with HIV-1 infection are not intrinsically more infectious to their contacts than are HIV-1-negative tuberculosis patients.

Adult tuberculosis in the 21st century: pathogenesis, clinical features, and management

This article reviews the significant advances in the past year in the basic and clinical aspects of adult tuberculosis (TB). Further research has deepened our understanding of host susceptibility and resistance mechanisms, including cytotoxicity, apoptosis, and antimicrobial polypeptides such as granulysin. Studies have confirmed the effects of HIV infection on risk of disease and disease manifestations, and have defined the effects of HIV on TB transmission. Recent studies also indicate a possible role for extended treatment of active disease and latent infection in HIV-1 infected individuals. Multidrug-resistant disease has been reported on every continent; rapid molecular approaches to the simultaneous diagnosis of TB and detection of rifampin resistance may facilitate prompt initiation of treatment. TB remains one of the major problems in global health.

Disclosure of HIV status: cultural issues of Asian patients

Disclosure of human immunodeficiency virus (HIV) status is a difficult emotional task creating opportunities for both support and rejection. For Asian patients there may be additional self-imposed barriers to disclosure that are rooted in cultural values. The purpose of this article is to describe how Asian cultural values of harmony and avoidance of conflict affect the disclosure experiences of HIV-positive Asian American and immigrants. Effective practice guidelines have been developed based on this information. Based on in-depth interviews with 16 HIV-positive Asian men, three focal issues were identified that serve as barriers to disclosure to family members: protection of family from shame, protection of family from obligation to help, and avoidance of communication regarding highly personal information. Additionally, patients felt disclosure was inhibited by the lack of HIV education to which families living overseas may have access. This is compounded by their lack of access to translated materials that they could send to family members. Similar to past disclosure research with non-Asian samples, the findings suggest that gay Asian men seek emotional support from gay friends. They would consider disclosing to relatives only when health reasons necessitated it. It is essential that helping professionals be attentive to the dishonor that patients may experience through disclosure and the stigma associated with being gay. Patients who are considering making a disclosure may need assistance with thinking through ways to provide HIV/acquired immune deficiency syndrome (AIDS) education to those family members that have little knowledge in this area. This may include translating or locating informational brochures translated into the family's language.

The contribution of recently acquired Mycobacterium tuberculosis infection to the New York City tuberculosis epidemic, 1989-1993

Current theory in the molecular epidemiology of tuberculosis holds that tuberculosis cases harboring Mycobacterium tuberculosis strains with a common deoxyribonucleic acid (DNA) fingerprint are the result of recent M. tuberculosis transmission. Here we propose a mathematical approach independent of DNA fingerprinting to estimating the percentage of recent transmissions responsible for current tuberculosis incidence. The "short-term reproductive number" of tuberculosis is defined as the average number of tuberculosis cases developing within 1 year of infection. Multiplying the short-term reproductive number by the number of tuberculosis cases in each year and dividing by the subsequent year's tuberculosis case burden equals the proportion of tuberculosis cases in the subsequent year that are due to recent transmission. We carried out separate calculations for human immunodeficiency virus (HIV)-negative and HIV-positive tuberculosis cases. We applied the model to pulmonary (infectious) tuberculosis cases diagnosed in New York City during 1989-1993, using tuberculosis and AIDS surveillance data. Model-based estimates of the proportion of tuberculosis due to recent transmission were lower than estimates based on DNA fingerprints. Reconciliation of these divergent estimates may require the re-estimation of model parameters from data collected de novo, additional model development, and further advances in DNA fingerprinting methods.

Infectiousness of Mycobacterium tuberculosis in HIV-1-infected patients with tuberculosis: a prospective study

BACKGROUND

Previous studies concerning the relative infectiousness of HIV-1-positive individuals with pulmonary tuberculosis have produced conflicting results. Thus, we assessed the effect of HIV-1 on the infectiousness of Mycobacterium tuberculosis in a prospective study.

METHODS

We organised in Santo Domingo, Dominican Republic, a cohort study of household contacts of HIV-1-positive and HIV-1-negative individuals with newly diagnosed pulmonary tuberculosis. Household contacts were assessed at their houses at baseline and followed up for 14 months for evidence of M tuberculosis infection and tuberculosis with a multi-step tuberculin skin test, anergy skin test, physical examinations, chest radiographs, and sputum smears.

FINDINGS

Tuberculin induration of 5 mm or greater was seen in 153 (61%) of 252 household contacts of HIV-1-positive index cases and in 418 (76%) of 551 household contacts of HIV-1-negative index cases (odds ratio 0.49 [95% CI 0.35-0.67], p=0.00001). In multivariate logistic-regression analysis after allowance for between-household variation in tuberculin response, HIV-1 infection of the index case remained inversely associated with the tuberculin response of the household contacts (0.52 [0.29-0.93], p=0.02). When the analysis was restricted to household contacts aged between 2 years and 15 years the adjusted association remained significant (0.37 [0.14-0.98], p=0.04). Among household contacts who had a negative tuberculin skin test at baseline, conversion to tuberculin skin test positivity was less frequent among household contacts of HIV-1-positive index cases (cut-off > or =5 mm: 32/131 [24%] vs 71/204 [35%], p=0.05; cut-off > or =10 mm: 23/153 [15%] vs 55/245 [22%], p=0.07).

INTERPRETATION

These data suggest that HIV-1-positive individuals with tuberculosis are less likely than HIV-1-negative individuals with tuberculosis to transmit M tuberculosis to their close contacts. No changes in the current policy regarding tuberculosis contact tracing are needed in the presence of HIV-1.

Tuberculosis and the HIV epidemic: increasing annual risk of tuberculous infection in Kenya, 1986-1996

OBJECTIVES

The purpose of this study was to assess the impact of the increased incidence of tuberculosis (TB) due to HIV infection on the risk of TB infection in schoolchildren.

METHODS

Tuberculin surveys were carried out in randomly selected primary schools in 12 districts in Kenya during 1986 through 1990 and 1994 through 1996. Districts were grouped according to the year in which TB notification rates started to increase. HIV prevalence in TB patients and changes in TB infection prevalence were compared between districts.

RESULTS

Tuberculous infection prevalence rates increased strongly in districts where TB notification rates had increased before 1994 (odds ratio = 3.1, 95% confidence interval = 2.3, 4.1) but did not increase in districts where notification rates had increased more recently or not at all. HIV prevalence rates in TB patients were 50% in districts with an early increase in notification rates and 28% in the other study districts.

CONCLUSIONS

Countries with an increasing prevalence of HIV infection will need additional resources for TB control, not only for current patients but also for the patients in additional cases arising from the increased risk of TB infection.

Granulomatous inflammation and the transmission of infection: schistosomiasis--and TB too?

Immune-dependent granulomatous inflammation is important in the pathogenesis of both schistosomiasis and tuberculosis. A case has previously been made for a role for schistosome egg-induced granulomas in the onward transmission of infection. Here, Mike Doenhoff suggests that a similar hypothesis applies to tuberculosis.

Tuberculosis risk in funeral home employees

In order to estimate the risk of tuberculosis infection among employees in the funeral service industry, we conducted a risk-assessment study of a convenience sample of funeral home employees. Study participants completed a risk-assessment questionnaire and underwent tuberculin skin testing. Of 864 employees tested, 101 (11.7%) had a reactive tuberculin skin test. Reactivity to the tuberculin skin test was significantly associated with job category; funeral home employees with a present or past history of embalming deceased-human remains were twice as likely to be reactive as were non-embalming personnel (14.9% versus 7.2%, P < 0.01). Reactivity was also associated with age, gender, race, past history of close contact with a person diagnosed with tuberculosis, and work history. After controlling for age and other factors, tuberculin reactivity was found to be associated in embalming personnel with the number of years spent performing embalmings (> or = 20), and, in non-embalming personnel, with a history of close contact with infected individuals. Based on these results, it is recommended that funeral home employees who routinely embalm cadavers undergo annual tuberculin skin testing, receive initial training on tuberculosis prevention, and wear respiratory protection when preparing known tuberculosis cases.