Comparison of children hospitalized with seasonal versus pandemic influenza A, 2004-2009

Abstract

BACKGROUND: The extent to which pandemic H1N1 influenza (pH1N1) differed from seasonal influenza remains uncertain. METHODS: By using active surveillance data collected by the Immunization Monitoring Program, Active at 12 Canadian pediatric hospitals, we compared characteristics of hospitalized children with pH1N1 with those with seasonal influenza A. We compared demographics, underlying health status, ICU admission, and mortality during both pandemic waves versus the 2004/2005 through the 2008/2009 seasons; influenza-related complications and hospitalization duration during pH1N1 wave 1 versus the 2004/2005 through the 2008/2009 seasons; and presenting signs and symptoms during both pH1N1 waves versus the 2006/2007 through the 2008/2009 seasons. RESULTS: We identified 1265 pH1N1 cases (351 in wave 1, 914 in wave 2) and 1319 seasonal influenza A cases (816 from 2006/2007 through 2008/ 2009). Median ages were 4.8 (pH1N1) and 1.7 years (seasonal influenza A); P