Estimating HIV-1 Incidence Using the Serologic Testing Algorithm for Recent HIV Seroconversion at HIV Counseling and Testing Centers in the City of Sao Paulo, Brazil

The network of HIV counseling and testing centers in Sao Paulo, Brazil is a major source of data used to build epidemiological profiles of the client population. In this study, HIV-1 incidence from November of 2000 to April of 2001 was estimated, comparing recently infected individuals to those with long-standing infection in terms of epidemiological and socio-behavioral aspects. To identify recent infection, less sensitive ELISA was employed. The overall incidence of HIV-1 infection among the clients was 0.53/100/year (95% CI: 0.31-0.85/100/year): 0.77/100/year for males (95% CI: 0.42-1.27/100/year) and 0.22/100/year (95% CI: 0.05-0.59/100/year) for females. Overall HIV-1 prevalence was 3.2% (95% CI: 2.8-3.7%), being 4.0% among males (95% CI: 3.3-4.7%) and 2.1% among females (95% CI: 1.6-2.8%). Recent infections accounted for 15% of the total (95% CI: 10.2-20.8%). Recent infection correlated with being younger and male (p = 0.019). Therefore, recent infection was more common among younger males and older females.