title: HIV-1 infection among female commercial sex workers in rural Thailand.
abstract: OBJECTIVE
  To reconstruct past HIV-1 incidence and identify risk factors for HIV-1 seroconversion among female commercial sex workers in a semi-rural setting in northern Thailand.
  
  
  METHODS
  Retrospective cohort of sex workers attending a sexually transmitted disease (STD) clinic at Mae Chan District Hospital, Chiang Rai Province, Thailand.
  
  
  METHODS
  Information included demographic data, HIV-1 antibody testing and STD diagnosis was collected in 821 sex workers attending the STD clinic from 1989 through 1993. HIV-1 incidence among initially HIV-1-seronegative sex workers who underwent repeat HIV-1 antibody testing during follow-up was determined and possible predictive factors for seroconversion including diagnosis of other STD were examined.
  
  
  RESULTS
  HIV-1 seroprevalence among 556 sex workers who underwent antibody testing was 52%, rising from 29% at initial test in 1989 to 53-63% for 1990-1993. Among 96 initially HIV-1-negative sex workers who underwent repeat testing, 64 HIV-1 seroconversions occurred, giving an incidence rate of 12.6/100 person months (PM). Incidence increased from 12.0/100 PM for 1989 and 1990 to 17.0/100 PM for 1991, with a subsequent decline to 9.3/100 PM for 1992-1993. The cumulative risk of seroconversion 6 months following initial negative HIV-1 antibody test was 57%. There were higher rates among younger sex workers (14-19 years old) and those from Hilltribes, but only a diagnosis of chancroid was significantly associated with HIV-1 seroconversion (P = 0.014).
  
  
  CONCLUSIONS
  An explosive epidemic of HIV-1 occurred among sex workers in a semi-rural area of northern Thailand from 1989. These HIV-1 incidence estimates, which are among the highest rates of sexual transmission ever reported, highlight the extreme vulnerability of female sex workers to HIV infection, even in a non-urban setting.
authors.affiliation: National Centre in HIV Epidemiology and Clinical Research, University of New South Wales, Sydney, Australia.
authors.forename: J A
authors.initials: JA
authors.lastname: Gray
authors.forename: G J
authors.initials: GJ
authors.lastname: Dore
authors.forename: Y
authors.initials: Y
authors.lastname: Li
authors.forename: S
authors.initials: S
authors.lastname: Supawitkul
authors.forename: P
authors.initials: P
authors.lastname: Effler
authors.forename: J M
authors.initials: JM
authors.lastname: Kaldor
mesh_terms: D000293:Adolescent; D000328:Adult; D000554:Ambulatory Care Facilities; D015331:Cohort Studies; D005260:Female; D015658:HIV Infections / Q000453:epidemiology*; D006679:HIV Seropositivity / Q000453:epidemiology; D015528:HIV Seroprevalence; D015497:HIV-1 / Q000276:immunology*; D006801:Humans; D015994:Incidence; D012189:Retrospective Studies; D012307:Risk Factors; D012424:Rural Population; D011477:Sex Work; D012749:Sexually Transmitted Diseases; D013785:Thailand / Q000453:epidemiology