Epidemiology of HIV-1 subtypes in an urban area of northern Italy

The distribution of the different subtypes of HIV varies from one region of the world to another. Subtype B is predominant in Europe and the USA, but there has been a gradual increase in non-B subtypes as a result of migration from regions where they are endemic, and this may have important implications for the control of HIV-1. The aim of this study was to assess the prevalence of HIV-1 subtypes in an urban area of northern Italy in the period 1997–2008. Forty-nine (12.2%; 95% CI, 9.00–15.40) of 401 patients investigated carried a non-B subtype, the prevalence of which was 7.7% (95% CI, 4.96–10.44) among native Italians and 55.3% (95% CI, 39.49–71.11) among non-Italians, 1.6% (95% CI, 0.00–3.81) among ex-intravenous drug addicts, 7.6% (95% CI, 1.21–13.99) among homosexual/bisexual men and 20.5% (95% CI, 14.83–26.17) among heterosexuals, 6.8% (95% CI, 3.37–10.23) among Italians infected as a result of sexual contacts in Italy, and 55.0% (95% CI, 33.20–76.80) among Italians infected abroad or by foreign partners. Overall prevalence increased from 2.9% (95% CI, 0.00–6.11) before 1993 to 23.0% (95% CI, 16.31–29.69) in the period 2001–2008. The results demonstrate that there has been an increase in non-B subtypes (especially sexually transmitted infections), particularly among patients infected abroad or by foreign partners.