Background: Eliminating syphilis is important not only to prevent the sequelae of infection but also to control the spread of HIV. Current prevention and control efforts in Canada have been ineffective in eliminating this disease.
Goal: The goal of the study was to determine the characteristics of individuals with infectious syphilis due to male-to-male and heterosexual contact, diagnosed during an outbreak in Calgary, Alberta, Canada.
Study design: This was a prospective study of individuals with infectious syphilis diagnosed at the STD clinic in Calgary between January 2000 and April 2002.
Results: The outbreak reported here (September 2000 to April 2002) involves 32 cases of infectious syphilis, corresponding to rates of 0.9/100,000 population during 2000 and 1.8/100,000 population during 2001. Between September 2000 and June 2001, the cases diagnosed were among men who have sex with men (MSM); between May 2001 and April 2002, they were due to locally acquired infections among heterosexuals, including one case of congenital syphilis. Compared to the heterosexuals, MSM tended to be older, be coinfected with HIV, and report excessive alcohol use (versus injection drug use) and had infectious syphilis diagnosed earlier. MSM used the Internet and bars or bathhouses to initiate sexual contact, whereas heterosexually acquired infections were largely among sex workers and their clients. Contact tracing was more successful among the heterosexuals than among MSM. The public health staff at the STD clinic initiated a series of multifaceted interventions in response to the outbreak. These interventions were moderately successful, as measured by the increased numbers of individuals seeking counseling and testing services at the clinic.
Conclusion: The results highlight key differences in the risk factor-specific characteristics of the outbreak that should be taken into account when designing prevention and control strategies.