Saturday, November 28, 2015

Social Network Investigation of a Syphilis Outbreak in Ottawa, Ontario

The incidence of syphilis in Ottawa, Ontario, has risen substantially since 2000 to six cases per 100,000 in 2003, again to nine cases per 100,000 in 2007, and recently rose to 11 cases per 100,000 in 2010. The number of cases reported in the first quarter of 2010 was more than double that in the first quarter of 2009.

In May 2010, the Ontario Ministry of Health and Long Term Care requested the assistance of the Field Epidemiology Program to describe the increase in infectious syphilis rates and to identify social network sources and prevention messages.

Syphilis surveillance data were routinely collected from January 1, 2009 to July 15, 2010, and social networks were constructed from an enhanced social network questionnaire. Univariate comparisons between the enhanced surveillance group and the remaining cases from 2009 on non-normally distributed data were conducted using Kruskal-Wallis tests and χ2 tests.

The outbreak cases were comprised of 89% men. Seventeen of the 19 most recent cases consented to answer the questionnaire, which revealed infrequent use of condoms, multiple sex partners and sex with a same-sex partner. Information regarding social venues where sex partners were met was plotted together with sexual partnerships, linking 18 cases and 40 contacts, representing 37% of the outbreak population and connecting many of the single individuals and dyads.

Uncovering the places sex partners met was an effective proxy measure of high-risk activities shared with infected individuals and demonstrates the potential for focusing on interventions at one named bar and one Internet site to reach a high proportion of the population at risk.

Below:  Reported infectious syphilis (primary, secondary and early latent cases only) rate per 100,000 population, males and females, Ottawa, Ontario, 2000 to 2009. Data source: Ontario Ministry of Health and Long-Term Care, integrated Public Health Information System, extracted December 23, 2014.

Below:   Reported infectious syphilis cases (primary, secondary and early latent cases only) by month and year of episode, Ottawa, Ontario, January 2009 to June 2010 (includes cases diagnosed up to June 15, 2010 (n=72) [includes only the earliest episode for four cases involving two episodes each of infectious syphilis in 2009 to 2010])

Full article at:

By:  H D’Angelo-Scott, PhD,1 J Cutler, MHSc,1 D Friedman, PhD,2 A Hendriks, MPH,2 and AM Jolly, PhD3
1Canadian Field Epidemiology Program, Public Health Agency of Canada;
2City of Ottawa Public Health, Centre for Communicable Disease and Infection Control;
3University of Ottawa, Ottawa, Ontario
Correspondence: Dr AM Jolly, Epidemiology and Community Medicine, University of Ottawa, Room 3105 Roger Guindon Hall, 451 Smyth Road, Ottawa, Ontario K1H 8M5. Telephone 613-562-5800 ext 8778, fax 613-562-5465, e-mail ac.awattou@ylloja

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