title: Increases in HIV incidence among men who have sex with men undergoing repeat diagnostic HIV testing in Ontario, Canada.
abstract: OBJECTIVE
  To estimate HIV incidence density for different exposure categories among people undergoing repeat testing in Ontario, Canada.
  
  
  METHODS
  Persons using voluntary, diagnostic HIV testing at least twice were identified by computerized and manual record linkage. In the 1992-2000 period, 980 seroconverters and 340 994 repeat negative testers contributed 936 145 person years (PY) of observation. Incidence density (ID) was calculated according to Kitayaporn et al. Poisson regression was used to evaluate differences in incidence.
  
  
  RESULTS
  Among men who have sex with men (MSM), ID declined between 1992-1996, from 1.23 per 100 PY in 1992 to 0.79 per 100 PY in 1996 [relative risk (RR), 0.86 per year; 95% confidence interval (CI), 0.77-0.96]. Subsequently, ID increased to 1.39 per 100 PY in 1999 (RR, 1.18 per year; 95% CI, 1.05-1.34). In 2000, ID was 1.16 per 100 PY but this decrease was not statistically significantly different from 1999. MSM in their twenties had the highest ID in 1992-1996, but in 1996-2000 MSM in their thirties had the highest risk of infection. Among injecting drug users (IDU), ID decreased from 0.64 per 100 PY in 1992 to 0.14 per 100 PY in 2000 (RR, 0.87 per year; 95% CI, 0.80-0.94). Among heterosexuals, annual incidence remained constant at about 0.03 per 100 PY in 1992-2000.
  
  
  CONCLUSIONS
  Increases in ID were identified among MSM from 1996 to 1999. These findings are consistent with other research. Continued vigilance and improved surveillance are needed to better understand and control the epidemic.
authors.affiliation: HIV Social, Behavioural and Epidemiological Studies Unit, Faculty of Medicine, University of Toronto, Ontario, Canada.
authors.forename: Liviana
authors.initials: L
authors.lastname: Calzavara
authors.forename: Ann N
authors.initials: AN
authors.lastname: Burchell
authors.forename: Carol
authors.initials: C
authors.lastname: Major
authors.forename: Robert S
authors.initials: RS
authors.lastname: Remis
authors.forename: Paul
authors.initials: P
authors.lastname: Corey
authors.forename: Ted
authors.initials: T
authors.lastname: Myers
authors.forename: Peggy
authors.initials: P
authors.lastname: Millson
authors.forename: Evelyn
authors.initials: E
authors.lastname: Wallace
mesh_terms: D015492:AIDS Serodiagnosis; D000328:Adult; D015658:HIV Infections / Q000175:diagnosis / Q000453:epidemiology*; D018451:Homosexuality, Male; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D009864:Ontario / Q000453:epidemiology; D011159:Population Surveillance; D015819:Substance Abuse, Intravenous