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. (C) 2006 Lippincott Williams & Wilkins.