Decline in the rate of genotypic resistance to antiretroviral drugs in recent HIV seroconverters in Madrid.

Genotypic resistance to antiretroviral drugs was analysed in plasma from 57 acute or recent HIV seroconverters in Madrid. The overall prevalence of drug-associated primary resistance mutations was 25.8% in 1997-1999, but declined to 3.8% in 2000-2001. The lower rate in recent years suggested that most new HIV infections derive from viraemic individuals unaware of their HIV- positive status, rather than from those failing antiretroviral treatment. Drug-resistance testing is thus not required before beginning antiretroviral therapy.