title: Mortality and transmissibility patterns of the 1957 influenza pandemic in Maricopa County, Arizona.
abstract: BACKGROUND
  While prior studies have quantified the mortality burden of the 1957 H2N2 influenza pandemic at broad geographic regions in the United States, little is known about the pandemic impact at a local level. Here we focus on analyzing the transmissibility and mortality burden of this pandemic in Arizona, a setting where the dry climate was promoted as reducing respiratory illness transmission yet tuberculosis prevalence was high.
  
  
  METHODS
  Using archival death certificates from 1954 to 1961, we quantified the age-specific seasonal patterns, excess-mortality rates, and transmissibility patterns of the 1957 H2N2 pandemic in Maricopa County, Arizona. By applying cyclical Serfling linear regression models to weekly mortality rates, the excess-mortality rates due to respiratory and all-causes were estimated for each age group during the pandemic period. The reproduction number was quantified from weekly data using a simple growth rate method and assumed generation intervals of 3 and 4 days. Local newspaper articles published during 1957-1958 were also examined.
  
  
  RESULTS
  Excess-mortality rates varied between waves, age groups, and causes of death, but overall remained low. From October 1959-June 1960, the most severe wave of the pandemic, the absolute excess-mortality rate based on respiratory deaths per 10,000 population was 16.59 in the elderly (≥65 years). All other age groups exhibit very low excess-mortality and the typical U-shaped age-pattern was absent. However, the standardized mortality ratio was greatest (4.06) among children and young adolescents (5-14 years) from October 1957-March 1958, based on mortality rates of respiratory deaths. Transmissibility was greatest during the same 1957-1958 period, when the mean reproduction number was estimated at 1.08-1.11, assuming 3- or 4-day generation intervals with exponential or fixed distributions.
  
  
  CONCLUSIONS
  Maricopa County exhibited very low mortality impact associated with the 1957 influenza pandemic. Understanding the relatively low excess-mortality rates and transmissibility in Maricopa County during this historic pandemic may help public health officials prepare for and mitigate future outbreaks of influenza.
authors: School of Human Evolution and Social Change, Arizona State University, Tempe, AZ, USA.|School of Life Sciences, Arizona State University, Tempe, AZ, USA.|Barrett, the Honors College, Arizona State University, Tempe, AZ, USA.
authors: April J
authors: AJ
authors: Cobos
authors: School of Human Evolution and Social Change, Arizona State University, Tempe, AZ, USA.|School of Life Sciences, Arizona State University, Tempe, AZ, USA.
authors: Clinton G
authors: CG
authors: Nelson
authors: School of Human Evolution and Social Change, Arizona State University, Tempe, AZ, USA.
authors: Megan
authors: M
authors: Jehn
authors: Division of International Epidemiology and Population Studies, Fogarty International Center, National Institutes of Health, Bethesda, MD, USA.
authors: Cécile
authors: C
authors: Viboud
authors: School of Human Evolution and Social Change, Arizona State University, Tempe, AZ, USA. gchowell@gsu.edu.|Division of International Epidemiology and Population Studies, Fogarty International Center, National Institutes of Health, Bethesda, MD, USA. gchowell@gsu.edu.|School of Public Health, Georgia State University, Atlanta, GA, USA. gchowell@gsu.edu.
authors: Gerardo
authors: G
authors: Chowell
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D001130:Arizona / Q000453:epidemiology; D002648:Child; D002675:Child, Preschool; D016208:Databases, Factual; D005260:Female; D049673:History, 20th Century; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D053121:Influenza A Virus, H2N2 Subtype / Q000302:isolation & purification; D007251:Influenza, Human / Q000453:epidemiology* / Q000266:history / Q000401:mortality / Q000635:transmission; D008875:Middle Aged; D009524:Newspapers as Topic; D058873:Pandemics; D015996:Survival Rate; D055815:Young Adult
keywords: 1957 influenza; Arizona; Asian influenza; H2N2 virus; Maricopa County; Mathematical epidemiology; Mortality rates; Reproduction number; Transmissibility