Mapping HIV transmission routes in rural Uganda, researchers project that outsiders frequently introduce the virus to communities and are more likely  to be the source of non-household transmission than other members of a specific community. Publishing their findings in PLOS Medicine, investigators analyzed data on nearly 15,000 individuals in 46 communities in Rakai District, Uganda.

The scientists calculated that, compared to the general population, the 1,597 people living with someone HIV positive were 3.2 times as likely to have HIV.

Analyzing the genetics of HIV samples, the researchers identified 95 clusters of genetic similarity among those living with the virus—suggesting that the virus passed between members within these respective clusters. Forty-four percent of these clusters (42/95) constituted two people living under one roof. Seventy-two percent of the rest of the clusters (38/52) connected people living in different communities, suggesting cross-community transmission of the virus.

The investigators estimated that 39 percent of new HIV transmissions in Rakai take place within stable partnerships within a household. Of those who are infected outside of such a relationship, 62 percent contract the virus from someone who does not life in their community.

The researchers cautioned that their findings are reliant on self reports and that they are not necessarily generalizable to regions outside of Rakai. They recommended prevention efforts that seek to impede cross-community transmission routes and to target populations who are likely transmitting the virus in this context.

To read the study, click here.