More than 35 million people around the world are infected with HIV and inside their bodies a devastating battle takes place between the immune system and the virus. "[Then] the virus is trapped between a rock and hard place, it can get flattened or make a change to survive and if it has to change then it will come with a cost," said Prof Philip Goulder, from the University of Oxford. We here investigate in Botswana and South Africa, countries severely affected by HIV, the impact on HIV virulence of adaptation of HIV to protective HLA alleles such as HLA-B*57. Drug bonus 
 
 The findings in Proceedings of the National Academy of Sciences also suggested anti-retroviral drugs were forcing HIV to evolve into milder forms. He said: "By comparing the epidemic in Botswana with that which occurred somewhat later in South Africa, the researchers were able to demonstrate that the effect of this evolution is for the virus to become less virulent, or weaker, over time.
– HIV has evolved into a less potent disease than it was 30 years ago, says a new study, and scientists say it might one day turn into a relatively harmless version of itself. British researchers drew the conclusions after studying HIV patients in Botswana and Africa, reports HealthDay. HIV arrived in Botswana a decade earlier than in South Africa, and today's version in Botswana is slower and less likely to cause AIDS. Twenty years ago, for example, the typical HIV patient in Botswana got AIDS in 10 years. Now it takes 12.5 years, "a sort of incremental change, but in the big picture that is a rapid change," says one of the lead researchers from the University of Oxford. As the BBC explains, scientists see it as a natural evolution: Eventually, HIV runs into people with natural immunity and has to adapt to survive, and this "watered down" version begins to spread. "In theory, if we were to let HIV run its course then we would see a human population emerge that was more resistant to the virus than we collectively are today," says a virologist at the University of Nottingham. "HIV infection would eventually become almost harmless," though he cautions that he's talking about "very large timescales." In its coverage, Reuters notes an HIV milestone: For the first time, the number of new annual infections is lower than the number of new HIV-positive people getting treatment, "meaning a crucial tipping point has been reached in reducing deaths from AIDS. "