Two randomised controlled trials of sexually transmitted disease (STD) treatment for the prevention of HIV-1 infection; in Mwanza; Tanzania and Rakai; Uganda; unexpectedly produced contrasting results. A decrease in population HIV-1 incidence was associated with improved STD case management in Mwanza; but was not associated with STD mass treatment in Rakai. Some reductions in curable STDs were seen in both studies. Theses trials tested different interventions in different HIV-1 epidemic settings and used different evaluation methods; the divergent results may be complementary rather than contradictory.

Possible explanations include:

differences in stage of the HIV-1 epidemic; which can influence exposure to HIV-1 and the distribution of viral load in the infected population; potential differences in the prevalence of incurable STDs (such as genital herpes); perhaps greater importance of symptomatic than symptomless STDs for HIV-1 transmission; and possibly greater effectiveness of continuously available services than of intermittent mass treatment to control rapid STD reinfection. Implications of the trials for policy and future research agenda are discussed