Circumcision and Cyberchase, revisited

This is me, last year, writing about a study on circumcision and HIV risk in Africa:

The study was stopped before its scheduled completion, because the reduction in risk was significant. But arguably, this reduction would itself reduce as the study went on longer -- men who maintained high-risk sexual activities might see a delay in infection with circumcision, but if those activities continued, they would likely ultimately be infected. In other words, we can't assume that the reduction in risk would project linearly with time. Instead, as time passes, the high-risk population would become increasingly saturated with infections. If this model held, then circumcision would become less and less effective over time.

This is from a press release about a current study showing that circumcision has less of an impact than thought last year:

The study has important policy implications. Several international AIDS organizations have begun to provide funding for male circumcisions as a deterrent to AIDS. While male circumcision may indeed reduce the risk of transmission by some 50% to 60% in each sexual encounter, reducing single encounter transmission rates alone cannot control the epidemic. The reason is that individuals in highly infected countries have multiple contacts with the infected so reducing transmission rates only defers the inevitable.

Now, the idea is that the rate of infection among prostitutes is the key factor, because it is the most important determinant of the long-term risk over many sexual encounters.