Developing surveillance for HIV transmission and risk behaviours among high-risk groups in a central London health district

Background Our aim was to describe surveillance data on HIV transmission and risk behaviours in Camden and Islington, an inner London health district (population 360 000). This information is required to assess the effectiveness of HIV-AIDS prevention. Methods We focused on two groups in the local population most severely affected by the HIV epidemic: homosexual and bisexual men, and injecting drug users. Data were drawn from routine and survey data, national and local sources, and a special local survey. Results There were estimated to be 9250 homosexual men, with an estimated prevalence of 7.7 per cent (confidence interval (CI) 5.9-11.0) diagnosed with HIV infection resident within the health district, and 9900 injecting drug users, with an estimated prevalence of 0.8 per cent (CI 0.6-1.1), diagnosed with HIV infection. New HIV infections diagnosed amongst homosexual men having a named test in HIV testing services averaged 281 and was unchanged between 1992 and 1996. However, unlinked anonymous seroprevalence surveys showed a decline in HIV prevalence for both homosexual men attending a genito-urinary medicine clinic and for injecting drug users attending services. Local surveys indicated that, in the preceeding year, one in three homosexual men had had unprotected anal intercourse with a man, and 13 per cent of intravenous drug users had shared equipment. There appeared to be no change in these levels over the years studied. Conclusion Population-based information on HIV is available at local level in England. It can be used for surveillance of HIV transmission and behaviour in high-risk groups, especially homosexual and bisexual men and intravenous drug users. Resources for HIV prevention are provided to all NHS districts, and surveillance is a cost-effective measure of the outcome of HIV prevention.