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.


METHODS
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.


CONCLUSIONS
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.
Egwaga
Saidi M
SM
National Tuberculosis and Leprosy Programme, Ministry of Health, Dar es Salaam, Tanzania.
Cobelens
Frank G
FG
Muwinge
Hemed
H
Verhage
Corry
C
Kalisvaart
Nico
N
Borgdorff
Martien W
MW
D017088:AIDS-Related Opportunistic Infections / Q000453:epidemiology* / Q000635:transmission*; D000293:Adolescent; D002648:Child; D003906:Developing Countries; D004196:Disease Outbreaks; D005260:Female; D015658:HIV Infections / Q000453:epidemiology; D006306:Health Surveys; D006801:Humans; D008297:Male; D015995:Prevalence; D013636:Tanzania / Q000453:epidemiology; D014374:Tuberculin Test; D014376:Tuberculosis / Q000453:epidemiology* / Q000635:transmission*