Targeting “hot zones” where the HIV epidemic is more severe and where the rate of sexual risk-taking is high is apparently a much more effective way to roll out the use of pre-exposure prophylaxis (PrEP) to prevent HIV. Researchers designed a computer model that mapped the varying rates of new HIV infections across South Africa and detected the hot zones. They used the model to project how the nation’s HIV infection rate would change if PrEP were promoted evenly throughout the nation or if it were targeted in the hot zones. The model suggests that, with the same number of PrEP users in each approach, the targeted strategy would prevent 40 percent more HIV cases than a blanket approach. The scientists say their model can be used to strategize PrEP delivery in other sub-Saharan African nations.