Impact of HIV on tuberculosis in northern Thailand

Introduction: The risk of tuberculosis is greatly increased in those with HIV infection, but the relative risk will vary over time, depending on the proportion of HIV-infected individuals with different levels of immunosuppression. This study in Chiang Rai. Thailand. assesses how this relative risk changes, investigates any interaction with age. and estimates the TB burden attributable to HIV infection now and in the future. Methods: We conducted a case-control study using retrospective data from Chiang Rai hospital. Cases were all newly diagnosed TB patients during 1990-1998. Controls were antenatal clinic attenders (ANC), delivery patients, surgical patients, blood donors and military conscripts. Odds ratios (OR) were calculated separately by year, age group and gender. using each control group separately. The population attributable fraction (PAF) was calculated by year. A mathematical model was developed to recalculate the PAF taking account of the time lag between HIV infection and TB, and to predict PAF in the future. Results: During the study period, the number of new TB cases in Chiang Rai hospital increased more than 3-fold. HIV prevalence peaked at 17.4% in 1992 in male military recruits before declining dramatically. The peak was later and lower in women. The OR for the association of TB and HIV infection increased markedly over time but there was no consistent pattern by age. Age-adjusted PAFs, rose to around 70% by 1998. Modelling suggested,that a true difference in ORs by age is masked by the lower proportion of individuals with more advanced HIV infection in younger age groups. The model gave slightly lower estimates for the PAF than those calculated directly, and predicted that the PAF would decline earlier in younger individuals. For older adults PAFs will remain very high throughout this decade. Conclusion: The HIV epidemic has a profound and prolonged impact on TB burden despite the marked reduction in HIV incidence already seen in Chiang Rai. Besides HIV prevention, we need additional TB control measures to reduce the burden among HIV positives

HIV and Tuberculosis in Ho Chi Minh City, Vietnam, 1997–2002

An emerging HIV epidemic, concentrated in young, male, injection drug users, is responsible for increasing TB reporting rates in urban Vietnam

The evolving epidemiology of HIV infection and tuberculosis in northern Thailand.

OBJECTIVES: To examine the association between HIV infection and tuberculosis (TB) and the proportion of TB attributable to HIV in Chiang Rai province, northern Thailand, in response to a rapidly changing incidence of HIV infection. METHODS: Case-control study covering the period 1990 to 1998. Cases were all new TB patients seen at Chiang Rai Hospital. Controls were antenatal clinic attendees, delivery patients, surgical patients, blood donors, and military conscripts. Odds ratios (ORs) were calculated by year, age group, and sex, using each control group separately. The population attributable fraction was calculated by year. RESULTS: During the study period, the number of new TB cases in Chiang Rai Hospital increased more than threefold. The ORs increased over time compared with all control groups for both sexes but did not vary consistently with age. The proportion of TB cases attributable to HIV rose to 72.0% in male patients and 65.8% in female patients by 1998. CONCLUSIONS: The HIV epidemic has a profound and prolonged impact on TB burden. Despite the marked reduction in HIV incidence already seen in Chiang Rai, the HIV prevalence among TB cases and the proportion of cases attributable to HIV continue to rise