Infections prevented by increasing HIV serostatus awareness in the United States, 2001 to 2004

Background: Persons living with HIV (PLWH) who are aware of their HIV status are more likely than serostatus-unaware PLWH to take precautions to prevent HIV transmission to their partners. The estimates of the Centers for Disease Control and Prevention (CDC) indicate that the proportion of PLWH who were aware of their serostatus increased between 2001 and 2004. The epidemiologic consequences of this increase in serostatus awareness are unknown. Methods: We developed a basic model of the US HIV epidemic from 2001 to 2004. Using this model, we calculated the number of incident infections that would have occurred in 2002 to 2004 had the proportion of PLWH who were aware of their serostatus remained at its 2001 level rather than increasing between 2001 and 2004. We then compared this incidence estimate with the CDCs estimated total of 120,000 incident infections in 2002 to 2004 to determine the number of infections prevented by the increase in serostatus awareness. Results: The increase from 2001 to 2004 in the proportion of PLWH who were aware of their serostatus can be credited with preventing nearly 6000 incident HIV infections in the 3-year period from 2002 to 2004. Sensitivity analyses indicated a plausible range of 4000 to 8700 prevented infections. Conclusion: This analysis demonstrates the important epidemio-logic benefits of increasing the proportion of PLWH who are aware of their HIV status.