Five-year group A streptococcal pharyngitis serotype surveillance in North America, 2000–2005

Abstract

The geographic and year–year heterogeneity of group A streptococcal (GAS) genotypes ( emm types) of isolates causing acute pediatric pharyngitis in North America have been poorly characterized. We established a network of 10 U.S. and 3 Canadian sites to collect isolates from children 3–18 years old with acute streptococcal pharyngitis. Collection began in 2000–2001, and the fifth year of collection was completed in May 2005. Multiple GAS types circulated simultaneously within each study site. Each year the 3 most prevalent emm types in the U.S. or Canada comprised 42–49% of all isolates nationally. The 6 most prevalent types each year consistently comprised 70–77% of isolates. Analysis of data from individual sites demonstrated considerable (in some instances striking) geographic variability as well as year–year variability. Differences were identified between the distribution of emm types from U.S. and Canadian sites. Continued pharyngeal emm type surveillance will be needed as multivalent M protein vaccine development proceeds.