Declining prevalence of HIV-1 drug resistance in antiretroviral treatment-exposed individuals in Western Europe

HIV-1 drug resistance represents a major obstacle to infection and disease control. This retrospective study analyzes trends and determinants of resistance in antiretroviral treatment (ART)-exposed individuals across 7 countries in Europe. Of 20,323 cases, 80\% carried at least one resistance mutation: these declined from 81\% in 1997 to 71\% in 2008. Predicted extensive 3-class resistance was rare (3.2\% considering the cumulative genotype) and peaked at 4.5\% in 2005, decreasing thereafter. The proportion of cases exhausting available drug options dropped from 32\% in 2000 to 1\% in 2008. Reduced risk of resistance over calendar years was confirmed by multivariable analysis.