title: High incidence of syphilis in HIV-positive homosexual men: data from two community-based cohort studies.
abstract: BACKGROUND
  Syphilis has re-emerged and become established in gay communities in most developed countries since the late 1990s. HIV infected men have been disproportionately affected by this endemic, but it is unclear whether this is due to behavioural or biological reasons. We report incidence and risk factors for syphilis in two community-based cohorts of HIV-negative and HIV-positive homosexual men in Sydney, Australia.
  
  
  METHODS
  Participants were recruited using similar community-based strategies in both cohorts and underwent annual face-to-face interviews. Syphilis screening was offered to all consenting participants at annual visits.
  
  
  RESULTS
  In the HIV-negative cohort, 21 men seroconverted to syphilis and one man had a syphilis re-infection during 2001-07, an incidence of 0.49 per 100 person-years (95% CI: 0.31-0.74). In the HIV-positive cohort during 2005-07, eight men seroconverted and one man had a syphilis re-infection, giving an incidence of 3.62 per 100 person-years (95% CI: 1.67-6.48). All nine reported a recent CD4 count of more than 350 cells microL(-1). Syphilis incidence was significantly higher in the HIV-positive cohort after adjustment for age (hazard ratio (HR) = 9.20, 95% CI: 3.63-23.31). Unprotected anal intercourse (UAI) with HIV-positive partners was significantly associated with incident syphilis in both cohorts (HR = 4.45, 95% CI: 1.37-14.45 in HIV-negative; HR = 8.67, 95% CI: 1.03-72.76 in HIV-positive).
  
  
  CONCLUSIONS
  Syphilis incidence was almost 10-fold higher in HIV-positive than in HIV-negative homosexual men, and it was not related to a CD4 count below 350 microL(-1). UAI with HIV positive partners was of particular importance in the transmission of syphilis.
authors.affiliation: National Centre in HIV Epidemiology and Clinical Research, University of New South Wales, Sydney, NSW 2010, Australia. jjin@nchecr.unsw.edu.au
authors.forename: Fengyi
authors.initials: F
authors.lastname: Jin
authors.forename: Garrett P
authors.initials: GP
authors.lastname: Prestage
authors.forename: Iryna
authors.initials: I
authors.lastname: Zablotska
authors.forename: Patrick
authors.initials: P
authors.lastname: Rawstorne
authors.forename: John
authors.initials: J
authors.lastname: Imrie
authors.forename: Susan C
authors.initials: SC
authors.lastname: Kippax
authors.forename: Basil
authors.initials: B
authors.lastname: Donovan
authors.forename: David J
authors.initials: DJ
authors.lastname: Templeton
authors.forename: John M
authors.initials: JM
authors.lastname: Kaldor
authors.forename: Andrew E
authors.initials: AE
authors.lastname: Grulich
mesh_terms: D000328:Adult; D015331:Cohort Studies; D015897:Comorbidity; D006679:HIV Seropositivity / Q000453:epidemiology*; D018451:Homosexuality, Male / Q000706:statistics & numerical data*; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D009517:New South Wales / Q000453:epidemiology; D012307:Risk Factors; D012309:Risk-Taking; D012747:Sexual Partners; D011795:Surveys and Questionnaires; D013587:Syphilis / Q000453:epidemiology*; D047568:Unsafe Sex / Q000706:statistics & numerical data*; D014505:Urban Population / Q000706:statistics & numerical data*