title: Timely assessment of the severity of the 2009 H1N1 influenza pandemic.
abstract: During the 2009 influenza pandemic, weekly mortality data were analyzed to estimate excess mortality above a seasonally adjusted baseline modeled from prior years' data. Between the 1962-1963 and 2008-2009 seasons, among persons ≥ 25 years old, excess mortality had been substantially higher during influenza A(H3N2)-dominant years than during A(H1N1)-dominant years. Among persons ≥ 15 years of age, excess mortality was higher in the 1968-1969 influenza pandemic season than during any other season. During the 2009-2010 pandemic, among all age groups <65 years old, excess mortality increased earlier than during any of the previous 47 seasons, eventually exceeding mortality in any prior non-pandemic season. In the ≥ 65-year-old age group, excess mortality remained relatively low, at rates typical of seasonal influenza A(H1N1) seasons. The model provided a timely assessment of severity during the 2009-2010 influenza pandemic, showing that, compared with prior seasons, mortality was relatively high among persons <65 years old and relatively low among those ≥ 65 years old.
authors.affiliation: Division of Viral Diseases, National Center for Immunization and Respiratory Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia 30333, USA.
authors.forename: Gregory L
authors.initials: GL
authors.lastname: Armstrong
authors.forename: Lynnette
authors.initials: L
authors.lastname: Brammer
authors.forename: Lyn
authors.initials: L
authors.lastname: Finelli
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D053118:Influenza A Virus, H1N1 Subtype / Q000302:isolation & purification*; D007251:Influenza, Human / Q000453:epidemiology* / Q000401:mortality* / Q000821:virology; D008297:Male; D008875:Middle Aged; D058873:Pandemics; D016019:Survival Analysis; D014481:United States / Q000453:epidemiology; D055815:Young Adult