Objective: To assess the seroprevalence of HIV-1 infection in homosexual and bisexual men in Nagoya City, Japan.
Design: A prospective study ongoing since April 1986.
Methods: Nine hundred and thirty-eight serum samples were collected from 531 participants in August 1990 in an anonymous, confidential testing programme. A self-administered questionnaire was completed and all participants anonymized by a code number. Interviews were conducted and HIV-antibody test results given by telephone, except for the positive test results, which were given in person and counselling offered.
Results: Two out of the 531 participants (0.38%) were found to be seropositive for HIV-1, although the seroprevalences of sexually transmitted diseases, including hepatitis B, syphilis, chlamydia infection and amoebiasis, were remarkably high. A small number of participants had had sexual contact with individuals from countries where HIV infection rates are high. No patient had had a recent episode of intravenous drug use. Numbers of male sexual partners were decreasing and unsafe sexual practices, such as anal intercourse without condom use, were also decreasing.
Conclusions: The apparent low-risk behaviour of the men studied here (low levels of sexual contact with foreigners, absence of intravenous drug use, decreasing numbers of sexual partners and unsafe sexual practices) may explain the low prevalence of HIV infection.