Case series descriptive analysis of a primary syphilis outbreak in Edmonton, Alberta, July 2004 - April 2006

Canada Communicable Disease Report

15 March 2007

Volume 33

Number 06

J Gratrix, MSc (1), L Honish, MSc (1), L Mashinter, MSc (candidate) (1), J Jaipaul, MN (1), B Baptiste, BScN (1), D Doering, BScN(1), J Talbot, MD (1)

  1. Public Health Division, Capital Health, Edmonton, Alberta

Syphilis is a sexually transmitted infection (STI) that has been notifiable in Canada since the 1940s. Rates of syphilis began declining in Canada in the early1980s, and by 1997 syphilis rates had met the national goal of elimination (< 0.5/100,000)(1).

Unfortunately, the continued elimination of syphilis has been hampered by recent outbreaks in subpopulations across Canada, contributing to rising rates nationally. After a syphilis outbreak among sex trade workers in Vancouver in mid-1997, local outbreaks were reported in other areas of Canada among men having sex with men in Calgary, Montreal, Ottawa and Toronto, as well as among heterosexuals in the Yukon(2). Subsequently, the national rate reported in 2004 was nine times the reported rate in 1997 (3.5 vs. 0.4 per 100,000)(3).

The last syphilis outbreak in Edmonton occurred in the early 1980s when over 1,000 cases of infectious syphilis were identified over a 7-year period(4); 2003 marked the first significant rise in infectious syphilis cases (primary, secondary and early latent stages) since that time. Twenty-seven cases of infectious syphilis were reported in the Capital Health region (Edmonton and surrounding area, Alberta, 2005 population 1,000,500(5)) in that year. Each subsequent year has seen a rise in the number of reported cases: 52 cases in 2004, 106 cases in 2005 and 36 cases identified during the first 3 months of 2006 (Figure 1). When analyzed by quarter, the epidemiologic curve depicts a smaller initial outbreak during 2003 and the first two quarters of 2004 followed by a second outbreak with a significant rise in cases beginning in the third quarter of 2004 and continuing to date. In addition, five babies born in 2005 had congenital syphilis, and one of the neonates died. To better understand the dynamics of the current outbreak, a case review was completed.

Figure 1. Quarterly reports of infectious syphilis cases, Edmonton (2003-2006)

Figure 1 - Quarterly reports of infectious syphilis cases, Edmonton (2003-2006)


To gain a greater understanding of the characteristics of the current syphilis outbreak in Edmonton, a descriptive case series analysis was undertaken through a review of client records held at the Capital Health Sexually Transmitted Diseases (STD) Centre. The STD Centre staff were uniquely suited to evaluate this outbreak, as over half of the cases (52.6%; n = 72) initially presented to the STD Centre for care, and the majority (82.5%; n = 113) were treated at the STD Centre. A syphilis case investigation is triggered by the provincial STD program when results are received from the provincial laboratory of reactive syphilis serology, or a positive direct fluorescent antibody or dark-field microscopy for Treponema pallidum. Investigations of Capital Health residents are forwarded to the STD Centre. An STD Centre nurse contacts the client to arrange for follow-up serologic tests, treatment, completion of a syphilis history and contact tracing. The syphilis history is returned to the provincial STD program, where the STD medical consultant confirms and stages all syphilis cases; the information is then entered into the provincial Communicable Disease Reporting System (CDRS).

Individuals who had primary syphilis infections diagnosed between 1 July, 2004, and 31 March, 2006, were selected for review from the provincial CDRS. Demographic variables, including age, sex, marital status (at time of diagnosis) and ethnicity were also retrieved from the database. The start date for the chart review (1 July, 2004) coincided with the significant rise in primary syphilis cases described earlier. Primary cases were selected because (a) this stage occurs nearest to the time of acquisition; (b) they offered the best client history related to risk factors; and (c) they represented 73% (n = 137) of all infectious syphilis cases (n = 187) reported during this time interval. Four public health nurses conducted chart reviews on 133 of the 137 primary cases that were identified; the remaining four cases did not have a chart at the STD Centre. Several behaviours of relevance to syphilis risk during the 6 months before diagnosis were included in the chart review: sexual preference, number of sexual contacts, unprotected sex, contact with commercial sex trade workers, STI co-infections, and injection and non-injection drug use. Lifetime history of STI and employment in the commercial sex trade were also reviewed. Any ambiguous information in the charts was discussed in the group of reviewers until they reached consensus on how the data would be interpreted. Variables were classified as unknown if the information was either missing from the chart or not reported by the client. Ethnicity-specific infection rates were calculated using 2001 Census data for the Capital Health region (Dr. J Edwards, Capital Health, Edmonton: personal communication, 2006).


The demographic features of all primary syphilis cases entered into the provincial CDRS (n = 137) are displayed in Table 1. Although 53% (n = 72) of all individuals reported their ethnicity as Caucasian, one half (n = 21) of all female cases were aboriginal (First Nations, Metis or Inuit). This ethnic disparity is reflected in the difference in incidence rates between aboriginal (95.4/ 100,000) and Caucasian females (4.7/100,000), demonstrating that infection rates were at least 20 times higher among aboriginal females. Similarly, incidence rates among aboriginal males (77.2/100,000) were six times higher than among Caucasian males (13.2/100,000).

Table 1. Demographic information on primary syphilis cases in Edmonton diagnosed between July 2004 and April 2006

  Number of subjects
Ethnicity Male (%) (n = 94) Female (%) (n = 43) Total (%) (n = 137)
Caucasian 53 (56.4) 19 (44.2) 72 (52.6)
Aboriginal (First Nations, Metis and Inuit) 17 (18.1) 21 (48.8) 38 (27.7)
Other 24 (25.5) 3 (7.0) 27 (19.7)
Incidence rate per 100,000
Caucasian (population 804,000) 13.2 4.7 9.0
Aboriginal (population 44,200) 77.2 95.4 86.0
Marital status
Single/widowed/divorced/separated 65 (69.1) 32 (74.4) 97 (70.8)
Married/common-law 16 (17.0) 6 (14.0) 22 (16.1)
Unknown 13 (13.8) 5 (11.6) 18 (13.1)
History of sexual behaviour
Heterosexual 85 (90.4) 38 (88.4) 123 (89.8)
Same-sex/bisexual 7 (7.4) 5 (11.6) 12 (8.7)
Unknown 2 (2.1) 0 2 (1.5)

Overall, the majority of cases (68.6%; n = 94) occurred among males; approximately one-third (31.4%; n = 43) were females. Cases were predominantly single (70.8%; n = 97) and ranged in age from 16 years to 83 years old. The mean age among males (42.7 [SD = 12.4] years) was significantly higher than among females (29.1 [SD = 9.8] years; t(135) = 6.3, p < 0.001).


Of the 133 charts reviewed, 90% (n = 123) of cases were heterosexual (Table 1). The average number of sexual partners was five, and 72.9% (n = 97) had had unprotected sexual contact in the 6 months before diagnosis (Table 2). Although a large proportion of cases (44.4%; n = 59) did not provide information regarding the geographic location at which they encountered their sexual contacts, 52 of the cases (39.1%) reported sexual contact in Edmonton.

Table 2. Characteristics of primary syphilis cases in Edmonton diagnosed between July 2004 and April 2006

  Number of subjects
Male (%) (n = 91) Female (%) (n = 42) Total (%) (n = 133)
Mean number of partners in previous 6 months 4.6 5.5 4.8
Location of sexual contact
Edmonton 40 (44.0) 12 (28.6) 52 (39.1)
Alberta (outside Edmonton) 4 (4.4) 1 (2.4) 5 (3.8)
Canada (outside Alberta) 1 (1.1) 0 1 (0.8)
International 5 (5.5) 0 5 (3.8)
Multiple locations 8 (8.8) 3 (7.1) 11 (8.3)
Unknown 33 (36.3) 26 (61.9) 59 (44.4)
Lifetime history of sex trade work
Yes 0 23 (54.8) 23 (17.3)
No 87 (95.6) 18 (43.9) 105 (78.9)
Uknown 4 (4.4) 1 (2.4) 5 (3.8)
History of contact with sex trade
Yes 26 (28.6) 0 26 (19.5)
No 41 (45.1) 30 (71.4) 71 (53.4)
Uknown 24 (26.4) 12 (28.6) 36 (27.1)
History of unprotected sex
Yes 67 (73.6) 30 (71.4) 97 (72.9)
No 8 (8.8) 3 (7.1) 11 (8.3)
Uknown 16 (17.6) 9 (21.4) 25 (18.8)
Mode of presentation
Contact tracing 11 (12.1) 11 (26.2) 22 (16.6)
Symptoms 71 (78.0) 20 (47.6) 91 (68.4)
Screening 9 (9.9) 11 (26.2) 20 (15.0)
Co-infection with HIV
Yes 6 (6.6) 0 6 (4.4)
No 81 (89.0) 42 (100) 123 (92.5)
Uknown 4 (4.4) 0 4 (3.0)
Co-infection with other STI
Yes 9 (9.9) 8 (19.0) 17 (12.8)
No 67 (73.6) 26 (61.9) 93 (69.9)
Uknown 15 (16.5) 8 (19.1) 23 (17.3)
Prior history of a STI
Yes 31 (34.1) 21 (50.0) 52 (39.1)
No 39 (42.9) 15 (35.7) 54 (40.6)
Uknown 21 (23.1) 6 (14.3) 27 (20.3)

More than one-third (36.8%; n = 49) of cases could be linked to the commercial sex trade: over half (54.8%; n = 23) of the female cases had been employed as sex trade workers, and nearly one-third (28.6%; n = 26) of male cases reported having contact with a sex trade worker (Table 2). The majority (52.2%; n = 12) of sex trade workers reported their ethnicity as aboriginal, followed by Caucasian (43.5%; n = 10) and black (4.3%; n = 1). Most sex trade workers (78.3%; n = 18) had a history of non-injection drug use, and over one-third (34.8%; n = 8) reported a history of injection drug use.

Although the majority (68.4%; n = 91) of cases presented to clinics with symptoms, one-quarter of female cases were identified through traditional contact tracing and routine screening. Six male cases were co-infected with human immunodeficiency virus (HIV): three had had a previous diagnosis of HIV infection, and three were newly HIV seropositive. Seventeen cases had a concurrent STI diagnosis, mostly for gonorrhea (47%; n = 8). Moreover, a third (39%; n = 52) of all cases had previously been infected with an STI: approximately one-half (46.2%; n = 24) of these individuals had had gonorrhea, and more than one-third (36.5%; n = 19) had had chlamydia in the past.

More than half (55.6%; n = 74) of cases had a history of non-injection drug use (Table 3). Of these cases, 55% (n = 37) reported the use of crack/cocaine, but alcohol (40%; n = 27) and marijuana (40%; n = 27) use was also reported frequently. Twenty-three of the cases reported a history of injection drug use, with crack/cocaine being the most frequently reported substance (n = 8).

Table 3. Substance use of primary syphilis cases

  Number of subjects
  Male (%) (n = 91) Female (%) (n = 42) Total (%) (n = 133)
History of non-injection drug use
Yes 43 (47.3) 31 (73.8) 74 (55.6)
No 34 (37.4) 6 (14.3) 40 (30.1)
Uknown 14 (15.4) 5 (11.9) 19 (14.3)
History of injection drug use
Yes 14 (15.4) 9 (21.4) 23 (17.3)
No 61 (67.0) 28 (66.7) 89 (66.9)
Uknown 16 (17.6) 5 (11.5) 21 (15.8)


Edmonton is continuing to experience this outbreak of infectious syphilis, with cases spreading into other communities in the province (Dr. A Singh, Alberta Health and Wellness, Edmonton: personal communication, 2006). The outbreak is predominantly characterized as involving older men and younger women. Cases were primarily identified as single, heterosexual and as having contacts largely in the Edmonton area. There is also an increased risk among the aboriginal population in Edmonton, accentuating the need to develop partnerships with the aboriginal community in order to heighten awareness and screen vulnerable groups.

Less than 20% of cases were identified through conventional contact tracing methods. Potential barriers to this process may be related to the finding that the majority of cases reported a history of substance abuse, possibly impairing their ability to identify partners. In addition, over one-third of cases were linked to the sex trade, making contact tracing difficult because of the anonymity of the sex trade environment. The number of cases linked to commercial sex trade activity within the 6 months preceding infection is likely an underestimation for several reasons: (a) secondary transmission from sex trade customers was not evaluated, (b) over one-quarter of cases were not asked about their contact with commercial sex trade workers and (c) there was likely reporting bias due to the social stigma associated with sex trade activity. Because traditional contact tracing methods have been minimally effective in the sex trade during this outbreak, the greatest challenge remains finding screening opportunities for those at highest risk. These may include accessing the plethora of sex trade venues, like massage parlours and escort services, or persons exchanging sexual activity for drugs. Obtaining assistance from our addiction counseling and treatment partners may also be beneficial.

Several initiatives have been undertaken in the Capital Health region in an attempt to control the outbreak. Although the majority of cases sought medical care for their symptoms, enlisting the assistance of the medical community in screening at-risk individuals is critical, as symptoms of syphilis are transient and lead to an asymptomatic phase. Consequently, letters were sent to physicians in the region regarding the resurgence of syphilis cases, the signs and symptoms of infection, and testing methods. A team of STD Centre outreach nurses and community health representatives (outreach workers) have also been working in inner city agencies and remand facilities to screen at-risk individuals and assist with the treatment of identified cases for those clients who may have difficulty accessing health services. The challenge that remains is reaching high-risk individuals who do not use the services and are not known to our partnering agencies.

Because other STIs are also transmitted through unprotected sexual contact, screening of clients who are at risk of syphilis should include STI and HIV screening as well. In this outbreak, over one-third of all cases (including half of the female cases) reported a history of STI. Moreover, in over 10% of clients another STI had been diagnosed at the time of their syphilis diagnosis. The STI testing status for 23 cases was unknown. Screening for HIV resulted in three new HIV diagnoses in this at-risk group.

Finally, as the number of younger women infected with syphilis increases in Edmonton, the risk of congenital syphilis rises concurrently. In 2005, four of the five mothers who delivered babies with congenital syphilis did not receive prenatal screening until the time of delivery. Thefifth mother was tested 2 months before delivery but could not be located for treatment. All of the babies were born prematurely and were taken into care by local children's services. All the mothers reported a history of substance use, and two also had a history of sex trade work. It is possible that these factors hindered their abilities to seek and receive adequate prenatal care.


Infectious syphilis continues to be a significant public health concern as the number of new infectious syphilis cases in Edmonton escalates. The urgent need to interrupt this outbreak is punctuated by the incidence of five congenital cases of syphilis, when the expected rate is zero. The information obtained from this data analysis is relevant in planning strategic interventions aimed at minimizing syphilis infection rates in the region.


The authors would like to acknowledge the Capital Health STD Centre, Edmonton.


  1. Public Health Agency of Canada. National goals for the prevention and control of sexually transmitted diseases in Canada. URL: < 97vol23/23s6nat/index.html>. Date of access: 8 November, 2006.

  2. Public Health Agency of Canada. 2002 Canadian sexually transmitted infections surveillance report. CCDR 2005;31(S2):1-39.

  3. Public Health Agency of Canada. 2004 Canadian sexually transmitted infections surveillance report: pre-release. URL: < x.html>. Date of access: 8 November, 2006.

  4. Romanowski B, Sutherland R, Love E et al. Epidemiology of an outbreak of infectious syphilis in Alberta. Int J STD AIDS 1991;2:424-7.

  5. Predy GN, Lightfoot P, Edwards J et al. How healthy are we? 2005 annual report of the Medical Officer of Health, March, 2006. Edmonton: Capital Health.

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