Curbing Appetites: In Uganda, the prevalence of HIV infection has fallen from 15% to 5% in the past ten years. The reason appears to be (surprise!) a decrease in promiscuity:

In the face of the then pervasive national campaign to encourage sticking to regular partners ('zero grazing' ...), reported multiple partner behaviour dropped noticeably. The Global Programme on AIDS surveys found that the proportion of men with one or more casual partners in the previous year fell from 35% in 1989 to 15% in 1995, and the proportion of women from 16% to 6%. Notably, the proportion of men reporting three or more non-regular partners fell from 15% to 3% (see bmj.com). "

Common sense works.