Epidemic of Invasive Pneumococcal Disease, Western Canada, 2005–2009 - Vol. 18 No. 5 - May 2012 - Emerging Infectious Disease journal - CDC
Table of Contents
Volume 18, Number 5–May 2012
Volume 18, Number 5—May 2012
Epidemic of Invasive Pneumococcal Disease, Western Canada, 2005–2009
Before the advent of antimicrobial drugs, outbreaks of invasive pneumococcal disease were numerous. Since then, however, outbreaks have been less frequently reported and have involved fewer persons, usually those confined to closed settings such as hospitals or military barracks (1,2). Even more rare have been large outbreaks or epidemics of invasive pneumococcal disease; if and when they do occur, they tend to be caused by a limited number of pneumococcal serotypes (2–4).
AbstractIn 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.
The serotype of a Streptococcus pneumoniae bacterium is designated according to the organism’s polysaccharide capsule, its major virulence factor. Worldwide, 91 polysaccharide capsular serotypes have been identified (5,6). A small subset of serotypes is responsible for most large outbreaks; these serotypes typically include, but are not restricted to, serotypes 1, 4, 5, 9V, 12F, and 23F (2).
Before 2005, large outbreaks of pneumococcal disease, including invasive pneumococcal disease caused by serotype 5, were rare in Canada. In 2002, an outbreak caused by S. pneumoniae in northern Quebec, Canada, was reported, and blood culture identified 10 cases as being caused by a serotype 1 strain (7). We report a large epidemic of invasive pneumococcal disease caused by S. pneumoniae serotype 5 in Canada that occurred during 2005–2009. The study received approval from the institutional research review committees of the health regions and the University of Alberta ethics review board.