Epidemic of invasive pneumococcal disease, western Canada, 2005-2009

Abstract

In Canada before 2005, large outbreaks of pneumococcal disease, including invasive pneumococcal disease caused by serotype 5, were rare. Since then, an epidemic of serotype 5 invasive pneumococcal disease was reported: 52 cases during 2005, 393 during 2006, 457 during 2007, 104 during 2008, and 42 during in 2009. Of these 1,048 cases, 1,043 (99.5%) occurred in the western provinces of Canada. Median patient age was 41 years, and most (659 [59.3%]) patients were male. Most frequently representing serotype 5 cases (compared with a subset of persons with non-serotype 5 cases) were persons who were of First Nations heritage or homeless. Restriction fragment-length polymorphism typing indicated that the epidemic was caused by a single clone, which multilocus sequence typing identified as sequence type 289. Large pneumococcal epidemics might go unrecognized without surveillance programs to document fluctuations in serotype prevalence.

Figure 1

Streptococcus pneumoniae serotype 5 isolated in western Canada, 2000–2009, by province and month. NT, Nunavut; PQ, Quebec; ON, Ontario; MN, Manitoba; SK, Saskatchewan, AB, Alberta; BC, British Columbia.

Figure 2

Total pneumococci serotyped in British Columbia, Alberta, Saskatchewan, and Manitoba, Canada, by month collected, 2000–2009. Gray bars represent all Streptococcus pneumoniae serotypes except serotype 5; black bars represent serotype 5 isolates only.

Figure 3

Age and sex of patients with invasive pneumococcal pneumonia caused by Streptococcus pneumoniae serotype 5, western Canada, 2000–2009. Median age 41 years.

Figure 4

Restriction fragment length polymorphism pattern of Streptococcus pneumoniae serotype 5 from epidemic in western Canada, 2000–2009 (epidemic clone), determined by pulsed-field gel electrophoresis. The Colombia⁵-19 strain is from the Pneumococcal Molecular Epidemiology Network (www.sph.emory.edu/PMEN) (17).