TY - JOUR
T1 - Mortality and transmissibility patterns of the 1957 influenza pandemic in Maricopa County, Arizona
AU - Cobos, April J.
AU - Nelson, Clinton G.
AU - Jehn, Megan
AU - Viboud, Cécile
AU - Chowell, Gerardo
N1 - Funding Information:
Acknowledgements We would like to thank the undergraduate students who assisted in collecting the raw data. April Cobos would like to thank Melinda Jenner for advice on mathematical modeling tools. This work was partially supported by the Multinational Influenza Seasonal Mortality Study (MISMS), an on-going international collaborative effort to understand influenza epidemiological and evolutionary patterns, led by the Fogarty International Center, National Institutes of Health (http://www.origem.info/misms/index.php).
PY - 2016
Y1 - 2016
N2 - 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.
AB - 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.
KW - 1957 influenza
KW - Arizona
KW - Asian influenza
KW - H2N2 virus
KW - Maricopa County
KW - Mathematical epidemiology
KW - Mortality rates
KW - Reproduction number
KW - Transmissibility
UR - http://www.scopus.com/inward/record.url?scp=84991759917&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=84991759917&partnerID=8YFLogxK
U2 - 10.1186/s12879-016-1716-7
DO - 10.1186/s12879-016-1716-7
M3 - Article
C2 - 27516082
AN - SCOPUS:84991759917
VL - 16
JO - BMC Infectious Diseases
JF - BMC Infectious Diseases
SN - 1471-2334
IS - 1
M1 - 405
ER -