In the United States, the number of AIDS cases attributed to heterosexual transmission, although still a small percentage of the total number of reported cases, is the most rapidly growing category. The rate at which HIV is transmitted between heterosexual couples and the factors that may impede or enhance heterosexual transmission are important to understanding and slowing the worldwide HIV epidemic.~This epidemiologic study is composed of three parts. PART A: In a prospective study, heterosexual couples who are discordant with respect to HIV infection will be evaluated at 6-month intervals to determine whether HIV transmission has occurred and to identify biological and behavioral factors associated with HIV transmission from the infected partner to the uninfected partner.~PART B: A case-control study will compare behavioral and biological data from heterosexual couples who are concordant for HIV infection at study entry with data from appropriate discordant couples enrolled in the prospective study. Cases will be HIV-infected secondary partners (from concordant couples) and controls will be uninfected secondary partners (from discordant couples).~PART C: In a cross-sectional study, semen and cervico-vaginal washings will be collected from HIV-infected men and women in Parts A and B and evaluated for presence of HIV by virologic and serologic methods.~Members of each couple will be interviewed separately by different interviewers. Demographic, sexual behavior and drug use history, and psychosocial information will be obtained. Participants will undergo clinical examination and various diagnostic laboratory tests (e.g., blood tests, urine screening, and gynecological tests). They will receive post-test counseling.
PRIMARY: To identify sexual behaviors and biological factors associated with an increased risk of heterosexual HIV transmission.~SECONDARY: To assess the effect of safer sex counseling on behavior of sexually active heterosexuals in which one member of the couple is infected with HIV. To create a repository of serum, peripheral blood mononuclear cells, semen, and cervico-vaginal washings from heterosexual couples who are concordant (both partners HIV infected) and discordant (one partner HIV infected) with respect to HIV infection.~In the United States, the number of AIDS cases attributed to heterosexual transmission, although still a small percentage of the total number of reported cases, is the most rapidly growing category. The rate at which HIV is transmitted between heterosexual couples and the factors that may impede or enhance heterosexual transmission are important to understanding and slowing the worldwide HIV epidemic.