Acquired immunodeficiency syndrome in low-incidence areas. How safe is unsafe sex?

Serum specimens from the cohort of persons who attended sexually transmitted disease clinics in New Mexico during a two-month period were tested for human immunodeficiency virus (HIV) antibody. Twenty-seven (2.0%) of 1374 serum specimens had repeatedly low-positive reactions by enzyme-linked immunosorbent assay testing, and 22 (1.6%) had repeatedly high-positive reactions. All sera (sufficient for testing by Western blot) with low-positive reactions gave negative results, and all sera (sufficient for testing by Western blot) with high-positive reactions gave positive results. All persons whose serum had high-positive reactions were male. Most (86%) had been seen at the only urban sexually transmitted disease clinic in New Mexico, and most (72%) were openly gay or bisexual. Of all gay and bisexual men evaluated, 14% (16/112) had high-positive reactions. Rapid plasma reagin positivity was significantly associated with HIV enzyme-linked immunosorbent assay low (false) positivity. The relatively high rate of HIV seropositivity among gay men with other sexually transmitted diseases indicates that transmission of acquired immunodeficiency syndrome is continuing in this low-incidence area and documents the need for testing and counseling programs in sexually transmitted disease clinics.