Factors that influence the virulence of HIV are of direct relevance to ongoing efforts to contain, and ultimately eradicate, the HIV epidemic. The authors here investigate the impact on HIV virulence of adaptation of HIV to protective HLA alleles such as HLA-B*57, in Botswana and South Africa, countries severely affected by HIV.

In Botswana, where the epidemic started earlier and reached higher adult seroprevalence than in South Africa, HIV replication capacity is lower. HIV is also better adapted to HLA-B*57, which in Botswana has no protective effect, in contrast to its impact in South Africa. Modelling studies indicate that increasing antiretroviral therapy access may also contribute to accelerated declines in HIV virulence over the coming decades.