RESUMO
The effect of injection-drug use on human immunodeficiency virus type 1 (HIV-1) env genetic evolution was examined in 15 seroconverting injection-drug users followed up for 4 years. After adjustment for non-drug-related independent variables significantly associated with genetic diversity (time since seroconversion and progressor status), injection frequency was positively and highly significantly associated with HIV-1 env genetic diversity (P=.003). The mutation rate in those who had injected at least once a day during the previous 6 months was estimated to be 62% greater than the rate in those who had not injected at all. If the positive effect of drug-injection frequency on env genetic diversity extends to the HIV-1 pol gene, the risk of emergence of resistance to antiretroviral drugs may be enhanced by increased drug-injection frequency, especially under the selection pressure of antiretroviral therapy.