National surveillance of HIV-1 subtypes for England and Wales - Design, methods, and initial findings

The HIV-1 infections detected in an ongoing national unlinked anonymous HIV surveillance program were subtyped and analyzed according to demographic a nd risk characteristics. Of the 893 anti-HIV-l-positive specimens allocated to an exposure group, 70% could be subtyped. Almost 25% of infections subt yped were non-B, mostly subtypes A, C, and D. Non-B infections were rare in homosexual and bisexual men and in drug injectors. Forty percent of infect ions in heterosexual men attending genitourinary medicine clinics were non- B subtypes; of these, 25% were subtype A infections and 59% were subtype C infections. For female clinic attendees, 61% were non-B subtype infections, of which 48% were subtype A infections and 42% were subtype C infections. Of the clinic attendees born in the United Kingdom and Europe, 14% of the m en and 35% of the women were infected with non-B subtypes. In contrast, 78% of infections in antenatal patients were non-B subtypes, of which 61% were subtype A and 29% were subtype C. Extrapolation to the estimated 29,700 pr evalent adult infections in the United Kingdom indicates that approximately 8,100 (27%) such infections are non-B subtypes and that these are found al most entirely in heterosexuals. The findings suggest spread of infection of non-B subtypes to heterosexuals born in the United Kingdom from individual s infected in regions of high prevalence.