Prevalence of human immunodeficiency virus in the patient population of a sexually transmitted disease clinic. Association with syphilis and gonorrhea.

An unlinked seroprevalence survey of human immunodeficiency virus (HIV) antibody was conducted using stored sera from all patients who attended the sexually transmitted disease (STD) clinic in Halifax, Nova Scotia between 1980 and 1986. None of the sera collected from 584 patients during 1980 were HIV positive. Of the 2867 patients who visited the clinic between 1981 and 1986, 27 (0.9%; 95% CI 0.6% to 1.2%) had the antibody. None of the 784 female patients were HIV seropositive. Of the 1,884 heterosexual men in the study, 5 (0.3%; 95% CI 0.1% to 0.5%) were HIV seropositive, and 22 (11.1%; 95% CI 6.7% to 15.5%) of the 199 homosexual men were HIV seropositive. There was a strong association between a history of syphilis and HIV antibody among heterosexual men (OR = 76.8; 95% CI 12.0 to 491.3; P = 0.001). Among homosexual men younger than 30 years of age, HIV infection was associated with a history of syphilis (OR = 18.2; 95% CI 5.1 to 64.7; P = 0.035) and a history of gonorrhea (OR = 8.2; 95% CI 4.2 to 16.0; P = 0.001). The association between a history of gonorrhea and HIV infection was strongest among homosexual men who had three or more sexual partners in the last month. These findings supplement existing evidence that STDs increase the likelihood of HIV transmission.