Current and future impact of HIV infection on tuberculosis morbidity (a case of Mumbai city in India).

A combination of human immunodeficiency virus (HIV) and tuberculosis (TB) has transgressed all boundaries of the globe and it is now clear from the fact that the incidence of tuberculosis is increasing rapidly with the increasing pace of HIV epidemic. This rapid increase was highest in the last 10 years in India and affected mostly the sexually active population in the city of Mumbai (also known as the AIDS capital of India). Therefore the assessment of the current and future impact of HIV on tuberculosis morbidity among sexually active population helps to have an appropriate plan for immediate control. A case-control study has been done in Sir J.J. Hospital & Grant Medical College Mumbai to examine the impact of HIV on tuberculosis among sexually active age-group individuals (15-49 years). Odds ratio and population attributable risks were used as basic tools to assess the proportion of tuberculosis cases that are attributed to HIV among both HIV infected and overall population. To estimate the future impact of HIV on tuberculosis the corresponding data are obtained from the Tuberculosis Control Programme (TCP) Brihanmumbai Municipal Corporation (BMC) Mumbai. A mathematical model has been used to predict the impact of HIV on tuberculosis which describes and predicts the annual rates of breakdown of TB disease for any arbitrary population in the age-group of 15-49 years. The estimates were obtained under three different scenarios. The model equations are based on actuarial method and are developed recursively by Schulzer et.al. in 1994. The vital input of the model incidence and prevalence rates of HIV was calculated using Epi-model package. The percentage of HIV sero positivity among tuberculosis patients increased significantly from 2.56 in 1988 to 22.7 in the year 1996 in Mumbai city. The results from a case-control study in the year 1996 reveal that the overall Mantel-Haenszel summary odds ratio for the impact of HIV on tuberculosis was found to be 3.1 (95% CI 2.04 - 4.08). This ratio has been varied according to different socio-demographic characteristics of the patients. The results indicate that the proportion of tuberculosis cases that are attributed to HIV among HIV infected is 68 (95% CI 50.9 – 75.4) per cent and is 17 (95% CI 12.8 – 19.1) per cent among the overall population. The results from the future impact of HIV on tuberculosis indicate that the intensity of increase in smear positivity rate increases with the increase in HIV incidence. The moderate scenario with HIV prevalence of 1.6% in the year 1998 would influx an estimate of increase at 129 per cent in smear positivity rates in the year 2000 relative to the pre-HIV year 1985 and the corresponding increase for the year 2005 is estimated at 278 per cent. One sixth of total tuberculosis cases in the age-group of 15-49 years are attributed to HIV in the population currently and the burden will increase by almost 3 fold by the year 2005 relative to the pre-HIV year 1985 with a dramatic increase in HIV associated sputum positive tuberculosis cases. In HIV prevention is the cure but in tuberculosis both prevention and cure are important. Curing more number of infectious (sputum positive) tuberculosis cases itself prevents the transmission of the disease. And it is equally important to take steps or explain the care for prevention of tuberculosis in the population. (authors)