Invasive group A streptococcal infections in Ontario, Canada

H. Dele Davies, Allison Mcgeer, Benjamin Schwartz, Karen Green, Darlene Cann, Andrew E. Simor, Donald E. Low

Research output: Contribution to journalArticlepeer-review

619 Scopus citations


Background: Several reports suggest that the incidence of invasive group A streptococcal infections, including streptococcal toxic shock syndrome and necrotizing fasciitis, is increasing. Methods: During 1992 and 1993 we conducted prospective, population-based surveillance of invasive group A streptococcal disease in Ontario, Canada. We reviewed clinical and laboratory records, searched for secondary cases of invasive disease, and cultured specimens from household contacts. Results: We identified 323 patients with invasive group A streptococcal infections, for an annual incidence of 1.5 cases per 100,000 population. The rates were highest in young children and the elderly. Fifty-six percent of the patients had underlying chronic illness. Risk factors for disease included infection with the human immunodeficiency virus, cancer, diabetes, alcohol abuse, and chickenpox. The most common clinical presentations were soft-tissue infection (48 percent), bacteremia with no septic focus (14 percent), and pneumonia (11 percent). Necrotizing fasciitis occurred in 6 percent of patients, and toxic shock in 13 percent. The mortality rate was 15 percent overall, but it was 29 percent among those over 64 years of age (P<0.001) and 81 percent among those with toxic shock (P<0.001). Fourteen percent of the cases were nosocomial, and 4 percent occurred in nursing home residents, often in association with disease outbreaks. Invasive disease occurred in 2 household contacts of patients with infection, for an estimated risk of 3.2 per 1000 household contacts (95 percent confidence interval, 0.39 to 12 per 1000). Conclusions: The elderly and those with underlying medical conditions are at greatest risk for invasive group A streptococcal disease, toxic shock, and necrotizing fasciitis. Invasive streptococcal infection is associated with a substantial risk of transmission in households and health care institutions.

Original languageEnglish (US)
Pages (from-to)547-554
Number of pages8
JournalNew England Journal of Medicine
Issue number8
StatePublished - Aug 22 1996
Externally publishedYes

ASJC Scopus subject areas

  • General Medicine


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