Per-contact probability of HIV transmission in homosexual men in Sydney in the era of HAART.

OBJECTIVE: The objective of this study is to estimate per-contact probability of HIV transmission in homosexual men due to unprotected anal intercourse (UAI) in the era of HAART. DESIGN: Data were collected from a longitudinal cohort study of community-based HIV-negative homosexual men in Sydney, Australia. METHODS: A total of 1427 participants were recruited from June 2001 to December 2004. They were followed up with 6-monthly detailed behavioral interviews and annual testing for HIV till June 2007. Data were used in a bootstrapping method, coupled with a statistical analysis that optimized a likelihood function for estimating the per-exposure risks of HIV transmission due to various forms of UAI. RESULTS: During the study, 53 HIV seroconversion cases were identified. The estimated per-contact probability of HIV transmission for receptive UAI was 1.43% [95% confidence interval (CI) 0.48-2.85] if ejaculation occurred inside the rectum, and it was 0.65% (95% CI 0.15-1.53) if withdrawal prior to ejaculation was involved. The estimated transmission rate for insertive UAI in participants who were circumcised was 0.11% (95% CI 0.02-0.24), and it was 0.62% (95% CI 0.07-1.68) in uncircumcised men. Thus, receptive UAI with ejaculation was found to be approximately twice as risky as receptive UAI with withdrawal or insertive UAI for uncircumcised men and over 10 times as risky as insertive UAI for circumcised men. CONCLUSION: Despite the fact that a high proportion of HIV-infected men are on antiretroviral treatment and have undetectable viral load, the per-contact probability of HIV transmission due to UAI is similar to estimates reported from developed country settings in the pre-HAART era.

Prevalence, incidence and risk factors for pharyngeal gonorrhoea in a community-based HIV-negative cohort of homosexual men in Sydney, Australia.

BACKGROUND: Pharyngeal gonorrhoea is common in homosexual men and may be important in maintaining community prevalence of anogenital infections. METHODS: From 2003, all participants in the Health in Men cohort of HIV-negative homosexual men in Sydney were offered annual pharyngeal gonorrhoea screening by BD ProbeTec nucleic acid amplification (NAAT) assay with supplementary porA testing. Participants self-reported diagnoses of pharyngeal gonorrhoea made elsewhere between interviews. Detailed sexual behavioural data were collected 6-monthly. RESULTS: Among 1427 participants enrolled, 65 study-visit-diagnosed pharyngeal gonorrhoea infections were identified (incidence 1.51 per 100 person-years, 95% CI 1.19 to 1.93) of which seven infections were identified on baseline testing (prevalence 0.57%, 95% CI 0.23 to 1.17%). Almost 85% of study-visit-diagnosed pharyngeal infections occurred without concurrent anogenital gonorrhoea. The combined incidence of study-visit-diagnosed and self-reported pharyngeal gonorrhoea (n=193) was 4.45 per 100 person-years (95% CI 3.86 to 5.12). On multivariate analysis, incident infection was associated with younger age (p-trend=0.001), higher number of male partners (p-trend=0.002) and reported contact with gonorrhoea (p<0.001). Insertive oro-anal sex ('rimming') was the only sexual behaviour independently associated with incident pharyngeal gonorrhoea (p-trend=0.044). CONCLUSIONS: The majority of pharyngeal gonorrhoea occurred without evidence of concurrent anogenital infection, and the high incidence-to-prevalence ratio suggests frequent spontaneous resolution of NAAT-detected infection. The association of pharyngeal gonorrhoea with oro-anal sex indicates that a broader range of sexual practices are likely to be involved in transmission of gonorrhoea to the pharynx than previously acknowledged. Screening the pharynx of sexually active homosexual men could play a role in reducing the prevalence of anogenital Neisseria gonorrhoeae.

Circumcision and risk of sexually transmissible infections in a community-based cohort of HIV-negative homosexual men in Sydney, Australia.

BACKGROUND: Circumcision status was examined as an independent risk factor for sexually transmissible infections (STIs) in the Health in Men cohort of homosexual men in Sydney. METHODS: From 2001 through 2004, 1427 initially human immunodeficiency virus (HIV)-negative men were enrolled and followed up until mid-2007. All participants were offered annual STI testing. The history of STIs was collected at baseline, and information on sexual risk behaviors was collected every 6 months. At annual face-to-face visits, participants reported STI diagnoses received during the previous year. RESULTS: Circumcision was not associated with prevalent or incident herpes simplex virus 1, herpes simplex virus 2, or self-reported genital warts. There was also no independent association of circumcision with incident urethral gonorrhea or chlamydia. Being circumcised was associated with a significantly reduced risk of incident (hazard ratio, 0.35 [95% confidence interval, 0.15-0.84]) but not prevalent (odds ratio, 0.71 [95% confidence interval, 0.35-1.44]) syphilis. The association was somewhat stronger among men who reported predominantly insertive unprotected anal intercourse (hazard ratio, 0.10 [95% confidence interval, 0.01-0.82]). CONCLUSIONS: These are the first prospective data obtained from homosexual men to assess circumcision status as a risk factor for STIs. Circumcised men were at reduced risk of incident syphilis but no other prevalent or incident STIs. Circumcision is unlikely to have a substantial public health impact in reducing acquisition of most STIs in homosexual men.

Trend in HIV incidence in a cohort of homosexual men in Sydney: data from the Health in Men Study.

OBJECTIVES: To determine the incidence of HIV seroconversion in a community-based cohort of homosexual men in Sydney from 2002 to 2006. METHODS: Participants were recruited between 2001 and 2004 from community-based events and venues. They were tested for HIV annually at follow-up interviews. Each year, the study database was matched against the national HIV register to identify additional HIV seroconversions among men lost to active follow up. The trend in HIV incidence over time was examined using Cox regression. RESULTS: Among 1426 participants, 52 cases of HIV seroconversion were identified between 2002 and 2006, an incidence of 0.87 per 100 person-years (95% CI: 0.65-1.14). HIV incidence varied from 1.67 per 100 person-years in 2002 to 0.39 in 2006 (P trend = 0.282). The median age of HIV seroconversion was 36.9 years, ranging from 22 to 63 years. CONCLUSION: In this community-based cohort of highly sexually active homosexual men in Sydney, HIV incidence was close to 1% each year and declined non-significantly between 2002 and 2006. These data are consistent with surveillance data suggesting no increase in recent HIV incidence in homosexual men in New South Wales.