Research shows that Drug-resistant HIV is set for a rapid upsurge
HIV is striking back against the antiretroviral drugs that keep it largely in check in rich countries, thanks both to its exposure to the major drugs and to individuals who don't realise they're infected and so spread resistant strains to new partners.
Drug-resistant strains of HIV have already been documented in San Francisco and elsewhere in the US, and Europe. Now a model of their transmission, based on studies of gay San Francisco men, forecasts a rapid upsurge in the next five years.
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.