Epidemiology of infectious syphilis in Ottawa. Recurring themes revisited.

Objectives: To describe the epidemiology of an outbreak of infectious syphilis in Ottawa.

Methods: A retrospective chart review of infectious syphilis cases in Ottawa from 2001-2006.

Results: Rates of syphilis have risen more than tenfold. The epidemic was centered in men, with the majority of cases (83.5%) occurring among men who have sex with men (MSM). These individuals differed from the general MSM population residing in Ottawa in their being older, more likely to be HIV positive, and more sexually promiscuous. Inconsistent condom use by MSM engaged in either oral or anal sex was pervasive. Thirty-seven percent of MSM reported sexual encounters with men from Montreal and Toronto. Visceral manifestations of syphilis, including neurosyphilis, were more common in persons co-infected with HIV. As a result, this subgroup was more likely to have received an extended antibiotic treatment regimen. There was a substantial delay between serological diagnosis and treatment. Less than half of treated cases returned for a six-month evaluation.

Conclusions: Multiple sexual partners, unprotected oral sex, and increased age among MSM were the predominant risk factors contributing to this syphilis epidemic. Co-infection with HIV modified the clinical presentation of syphilis, necessitating a more intensive diagnostic and therapeutic approach. The interconnection of urban sexual networks has likely contributed to the dynamics of local syphilis transmission and suggests that effective interventions will require a coordinated national approach.