title: Probability of female-to-male transmission of HIV-1 in Thailand.
abstract: The epidemic of human immunodeficiency virus type 1 (HIV-1) infection in Thailand has allowed an estimate to be made of the probability of female-to-male HIV-1 transmission per sexual contact. In a study of 1115 21-year-old male military conscripts, of whom 77 (6.9%) were HIV-1 seropositive, sex with female prostitutes was identified as the principal mode of HIV-1 transmission. With a mathematical model including data on conscript's age at first sexual contact, frequency of sex with female prostitutes, and province of origin; as well as province-specific HIV-1 seroprevalence of prostitutes, we estimated the probability of HIV-1 transmission per sexual contact to be 0.031 (95% confidence limits [CL] 0.025-0.040). Allowing for random error in the self-reported frequency of contacts, the estimate was 0.056 (95% CL 0.041-0.075). The transmission probability was significantly greater among men with a history of sexually-transmitted diseases. These estimates are substantially higher than analogous estimates made in North America. This high per-act probability of heterosexual transmission helps to explain the rapid spread of HIV-1 in the emerging epidemic in Thailand and perhaps in other countries where HIV-1 transmission is predominantly heterosexual.
authors.affiliation: HIV/AIDS Collaboration, Bangkok, Thailand.
authors.forename: T D
authors.initials: TD
authors.lastname: Mastro
authors.forename: G A
authors.initials: GA
authors.lastname: Satten
authors.forename: T
authors.initials: T
authors.lastname: Nopkesorn
authors.forename: S
authors.initials: S
authors.lastname: Sangkharomya
authors.forename: I M
authors.initials: IM
authors.lastname: Longini
mesh_terms: D000328:Adult; D015982:Bias; D015897:Comorbidity; D016001:Confidence Intervals; D005260:Female; D015658:HIV Infections / Q000097:blood / Q000453:epidemiology* / Q000517:prevention & control / Q000635:transmission*; D015528:HIV Seroprevalence; D015497:HIV-1; D006801:Humans; D016013:Likelihood Functions; D008297:Male; D008889:Military Personnel; D015233:Models, Statistical; D011159:Population Surveillance; D011446:Prospective Studies; D012111:Residence Characteristics; D012307:Risk Factors; D016036:Seroepidemiologic Studies; D017678:Sex Distribution; D011477:Sex Work; D012725:Sexual Behavior; D012749:Sexually Transmitted Diseases / Q000453:epidemiology* / Q000382:microbiology / Q000517:prevention & control; D013785:Thailand / Q000453:epidemiology