Spread of HIV infection in a rural area of Tanzania

Objective: To assess the spread of HIV into rural areas. Methods: Since 1994 a demographic surveillance system (with 5-monthly round s) and open adult cohort study have been established in a rural ward in Tan zania. Two sero-surveys of all resident adults aged 15-44 and 15-46 years w ere conducted in 1994-1995 and 1996-1997 respectively. Qualitative data wer e collected on mobility, bars and commercial sex. Results: Attendance of the two rounds of survey was 5820 (78%) and 6413 (80 %) in 1994/1995 and 1996/1997 respectively. HIV prevalence increased from 5 .8% to 6.6%. HIV incidence was 0.73 and 0.84 per 100 person years among men and women respectively. HIV incidence under the age of 20 years was low am ong both sexes. Striking differences in HIV prevalence and incidence were o bserved within the small geographic area studied: HIV prevalence in the tra ding center was twice that in the area surrounding the trading center (with in 2 km) and three to four times that in the rural villages (within 8 km of the trading center). Aggregate level data showed significant differences b etween the trading center and nearby rural villages in terms of sexual beha vior, commercial sex workers, mobility of the population, and alcohol use. Conclusion: This study documents the existence of very substantial HIV prev alence and incidence differences within a small geographic rural area. The rapid decrease in HIV prevalence within a small rural area emphasizes the i mportance of concentrating HIV prevention efforts on high transmission area s, such as trading centers, especially in resource-poor settings. Furthermo re, this has considerable implications for monitoring the spread of HIV thr ough sentinel sites, as such sites are typically located in high transmissi on areas. (C) 1999 Lippincott Williams & Wilkins.