ARCHIVED: E-SYS Quick Facts – Chlamydia: A hidden epidemic in Canadian street youth


Chlamydia: A Hidden Epidemic in Canadian Street Youth
Chlamydia: A Hidden Epidemic in Canadian Street Youth
Cat. No HP5-15/2006E-PDF
ISBN 0-662-43488-9

PDF version - 4 pages, 65 kb

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Street youth are a marginalized and vulnerable segment of the population. There are an estimated 150,000 street youth in Canada on any given day.1

Among street youth, unprotected sex, sex with multiple partners and unsafe drug use behaviours, such as sharing drug injection equipment, increase the risk of contracting and transmitting sexually transmitted infections (STIs) and blood-borne infections (BBIs). Chlamydia is an example of an STI that is common among street youth.

The information presented in this overview is based on the 1999, 2001 and 2003 data collection cycles of Enhanced Surveillance of Canadian Street Youth (E-SYS). E-SYS is a multi-centre sentinel surveillance system that monitors rates of STIs and BBIs, risk behaviours and health determinants in the Canadian street youth population.

Chlamydia is 10 times more common in street youth than in general population youth

Figure 1 shows that

  • The prevalence* of chlamydia among street youth is about 10 times higher than among youth in the general population.4
  • The prevalence rate for chlamydia among street youth participating in E-SYS increased from 8.6% in 1999 to 11.3% in 2003.
  • In contrast, the prevalence rate for chlamydia rose very slightly from 0.7% to 0.9% among general population youth during the same time period.
  • Chlamydia rates are higher in female street youth than in their male counterparts.

The propensity of street youth to engage in extremely risky sexual behaviours, such as unprotected sex with high-risk partners, likely accounts for the high prevalence of chlamydia in this population.

“E-SYS is a collaboration between the Public Health Agency of Canada’s Surveillance and Epidemiology Unit (Community Acquired Infections Division, Centre for Infectious Disease Prevention and Control), Health Canada’s Office of Research and Surveillance (Drug Strategy and Controlled Substances Program), participating surveillance sites and the youth who provide the data and samples collected.”

Figure 1. Prevalence of chlamydia among street youth in 1999, 2001 and 2003

Figure 1. Prevalence of chlamydia among street youth in 1999, 2001 and 2003

High-risk sexual behaviours: A gateway to chlamydia infection

  • In 2003, the prevalence rate for chlamydia was significantly higher in E-SYS street youth who reported no condom use at their last sexual encounter with a female sex partner than in those who reported using a condom (12.2% compared to 8.7% respectively).
  • In 2003, street youth who tested positive for chlamydia had on average more paying sexual partners** per week than youth who tested negative (19 partners compared to 8 partners respectively). In 1999, street youth who reported that they had been previously diagnosed with an STI had significantly higher rates of chlamydia than those who reported no previous STI diagnosis (11.7% compared to 7.8%).
    • This association was again found in 2001 and 2003, although only among street youth aged 15-19 years.
  • Findings from E-SYS further revealed that street youth usually did not change their sexual behaviours after the diagnosis of an STI.


Findings from E-SYS show that the prevalence of chlamydia in street youth is exceptionally high when compared to youth in the general population. In addition, it is apparent that among street youth, females are disproportionately affected by chlamydia.

Chlamydia is a treatable STI, and the unnecessary consequences of untreated chlamydia infection can be averted. Targeting street youth and providing them with counselling and incentives - especially to females - to modify their sexual behaviour is essential to addressing this problem. This is crucial, as E-SYS has revealed that street youth do not tend to modify their behaviour even if diagnosed with an STI. Further research on street youth, particularly on innovative ways to reduce the transmission and spread of chlamydia, is needed. Ongoing surveillance is also required to monitor and assess progress if the goal of reducing chlamydia infections and other STIs in street youth is to be achieved.


For further information please contact:
Surveillance and Epidemiology Section
Community Acquired Infections Division (CAID)
Centre for Infectious Disease Prevention and Control (CIDPC)
Public Health Agency of Canada (PHAC)
AL 0603B
Ottawa, ON K1A 0K9
Tel. 613-946-8637
Fax. 613-946-3902


* Rates in street youth are prevalence rates; the general population youth rates they are compared to are derived from reported cases. Rates from reported cases may underestimate the actual prevalence in the general population, due to symptomatic cases and those who do not report for testing.

** Paying partners refers to partners who pay youth in return for sex.

  1. DeMatteo D, et al. Toronto Street Youth and HIV/AIDS: Prevalence, Demographics, and Risks. Journal of Adolescent Health. 1999; 25(5): 358-366.
  2. Shields S, et al. Prevalence and Correlates of Chlamydia Infection in Canadian Street Youth. Journal of Adolescent Health. 2004; 34: 384-390.
  3. Centres for Disease Control and Prevention. Trends in Reportable Sexually Transmitted Diseases in the United States, 2004; National Surveillance Data for Chlamydia, Gonorrhea, and Syphilis.
  4. Public Health Agency of Canada. 2002 Canadian Sexually Transmitted Infections Surveillance Report. Canada Communicable Disease Report (CCDR). 2005; 31: S2.

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