Drug-resistant strains of HIV could become more prevalent - even developing into mini-epidemics - in San Francisco over the next five years as patients live longer, healthier lives, according to a study by researchers at UCSF and UCLA.

San Francisco public health officials emphasized that drug-resistant HIV is not a health crisis and said that while the study is interesting, they don't expect it to change how doctors treat people with HIV infections.

Currently, people with HIV tend to be given a cocktail of drugs, making it less likely that resistance will emerge. That's because even if a strain evolves resistance to one of the drugs, it will still succumb to the others.

However, the virus can evolve resistance nonetheless. Currently, about 15 per cent of new infections in San Francisco are from resistant strains, some of them resistant to all three major classes of drug used to combat the virus.

More at San Francisco Gate and New Scientist