title: Sexual transmission of HIV-1 among injection drug users in San Francisco, USA: risk-factor analysis.
abstract: BACKGROUND
  Many new HIV-1 infections in the USA occur in injection drug users (IDUs). HIV-1seroconversion of IDUs is mainly associated with injection-related risk factors. Harm- reduction programmes concentrate on injection-risk behaviour. We aimed to establish whether injection or sexual risk factors, or both, were associated with HIV-1antibody seroconversion of street-recruited IDUs in San Francisco, from 1986 to 1998.
  
  
  METHODS
  IDUs were enrolled every 6 months from four community sites. We did a nested case-control study comparing 58 respondents who seroconverted between visits with 1134 controls who remained seronegative. Controls were matched with cases by sex and date. Adjusted odds ratios and 95% CI were calculated for men and women by use of conditional logistic regression.
  
  
  RESULTS
  Men who had sex with men were 8.8 times as likely to seroconvert (95% CI 3.7-20.5) as heterosexual men. Women who reported having traded sex for money in the past year were 5.1 times as likely as others to seroconvert (95% CI 1.9-13.7). Women younger than 40 years were more likely to seroconvert than those 40 years or older (2.8 [1.05-7.6]), and women who reported having a steady sex-partner who injected drugs were less likely to seroconvert than other women (0.32 [0.11-0.92]).
  
  
  CONCLUSIONS
  HIV-1 seroconversion of street-recruited IDUs in San Francisco is strongly associated with sexual behaviour. HIV-1risk might be reduced by incorporation of innovative sexual-risk-reduction strategies into harm-reduction programmes.
authors.affiliation: Urban Health Study, Institute for Health Policy Studies and Departments of Family and Community Medicine, UCSF, 3180 18th Street, San Francisco CA 94110, USA. alkral@itsa.ucsf.edu
authors.forename: A H
authors.initials: AH
authors.lastname: Kral
authors.forename: R N
authors.initials: RN
authors.lastname: Bluthenthal
authors.forename: J
authors.initials: J
authors.lastname: Lorvick
authors.forename: L
authors.initials: L
authors.lastname: Gee
authors.forename: P
authors.initials: P
authors.lastname: Bacchetti
authors.forename: B R
authors.initials: BR
authors.lastname: Edlin
mesh_terms: D000328:Adult; D016022:Case-Control Studies; D005260:Female; D015658:HIV Infections / Q000635:transmission*; D006679:HIV Seropositivity; D015497:HIV-1; D006801:Humans; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D012307:Risk Factors; D012495:San Francisco; D012725:Sexual Behavior; D015819:Substance Abuse, Intravenous