title: Severe mortality impact of the 1957 influenza pandemic in Chile.
abstract: Epidemiological studies of the 1957 influenza pandemic are scarce, particularly from lower-income settings.
  
  
  
  We analyzed the spatial-temporal mortality patterns of the 1957 influenza pandemic in Chile, including detailed age-specific mortality data from a large city, and investigated risk factors for severe mortality impact across regions.
  
  
  
  Chile exhibited two waves of excess mortality in winter 1957 and 1959 with a cumulative excess mortality rate of 12 per 10 000, and a ~10-fold mortality difference across provinces. High excess mortality rates were associated with high baseline mortality (R2=41.8%; P=.02), but not with latitude (P>.7). Excess mortality rates increased sharply with age. Transmissibility declined from R=1.4-2.1 to R=1.2-1.4 between the two pandemic waves.
  
  
  
  The estimated A/H2N2 mortality burden in Chile is the highest on record for this pandemic-about three to five times as severe as that experienced in wealthier nations. The global impact of this pandemic may be substantially underestimated from previous studies based on high-income countries.
authors.affiliation: Georgia State University, Atlanta, Georgia, USA.|Fogarty International Center, National Institutes of Health, Bethesda, MD, USA.
authors.forename: Gerardo
authors.initials: G
authors.lastname: Chowell
authors.affiliation: Fogarty International Center, National Institutes of Health, Bethesda, MD, USA.|George Washington University, Washington DC, USA.|University of Copenhagen, Copenhagen, Denmark.
authors.forename: Lone
authors.initials: L
authors.lastname: Simonsen
authors.affiliation: Ministerio de Salud, Santiago, Chile.
authors.forename: Rodrigo
authors.initials: R
authors.lastname: Fuentes
authors.affiliation: The University of South Dakota, Vermillion, SD, USA.|Universidad de Chile, Santiago, Chile.
authors.forename: Jose
authors.initials: J
authors.lastname: Flores
authors.affiliation: Fogarty International Center, National Institutes of Health, Bethesda, MD, USA.
authors.forename: Mark A
authors.initials: MA
authors.lastname: Miller
authors.affiliation: Fogarty International Center, National Institutes of Health, Bethesda, MD, USA.
authors.forename: Cécile
authors.initials: C
authors.lastname: Viboud
mesh_terms: D000293:Adolescent; D000328:Adult; D017677:Age Distribution; D000368:Aged; D002648:Child; D002675:Child, Preschool; D002677:Chile / Q000453:epidemiology; D005260:Female; D006801:Humans; D009980:Influenza A virus / Q000145:classification / Q000235:genetics / Q000302:isolation & purification*; D007251:Influenza, Human / Q000453:epidemiology / Q000401:mortality* / Q000821:virology; D008875:Middle Aged; D058873:Pandemics; D012621:Seasons; D055815:Young Adult
keywords: 1957 influenza pandemic; Chile; baseline mortality rates; excess mortality rates; latitude; reproduction number; transmissibility