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BMC Infect Dis. 2016 Aug 11;16(1):405. doi: 10.1186/s12879-016-1716-7.
Mortality and transmissibility patterns of the 1957 influenza pandemic in Maricopa County, Arizona.
Cobos AJ1,2,3, Nelson CG1,2, Jehn M1, Viboud C4, Chowell G5,6,7.
Author information
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.
KEYWORDS:
1957 influenza; Arizona; Asian influenza; H2N2 virus; Maricopa County; Mathematical epidemiology; Mortality rates; Reproduction number; Transmissibility
PMID: 27516082 DOI: 10.1186/s12879-016-1716-7
[PubMed - in process]
Mortality and transmissibility patterns of the 1957 influenza pandemic in Maricopa County, Arizona.
Cobos AJ1,2,3, Nelson CG1,2, Jehn M1, Viboud C4, Chowell G5,6,7.
Author information
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.
KEYWORDS:
1957 influenza; Arizona; Asian influenza; H2N2 virus; Maricopa County; Mathematical epidemiology; Mortality rates; Reproduction number; Transmissibility
PMID: 27516082 DOI: 10.1186/s12879-016-1716-7
[PubMed - in process]