Projection of HIV infection in Calcutta.

Starting with the base year of 1991, the HIV infection projection for 1992-99 for the total, as well as various high-risk sub-populations of Calcutta, the first of its kind is provided. These projections are based on statistical methodology developed in this paper. Our methodology for spread of HIV infection takes into account various social interactions and practices and also uses available data. Rates of these interactions and practices and estimates of demographic parameters used in making projections were obtained primarily from surveys and census data. Since one of these estimated rates, that of HIV transmission rate through heterosexual encounters between an infected and an uninfected had a large range, we have provided two sets of projections based on the largest of these rates (worst-case scenario) and another that is consistent with the available data. The total projection of the number of HIV infected cases in Calcutta for 1999 is between 49,000 and 1,26,000. Separate projections are also provided for high-risk sub-groups. Among these, the sex workers expectedly will continue to manifest the highest numbers of newly infected cases. The temporal rate of increase in prevalence is projected to be alarmingly higher in the general population than even among sex workers, although the actual prevalence will continue to be the lowest in the general population compared to all other sub-groups of the population.