a1 Fogarty International Center, National Institutes of Health, Bethesda, MD, USA
a2 Department of Pediatrics, Keiyu Hospital, Yokohama, Japan
a3 Department of Global Health, School of Public Health and Health Services, George Washington University, Washington, DC, USA
Historical studies of influenza pandemics can provide insight into transmission and mortality patterns, and may aid in planning for a future pandemic. Here, we analyse historical vital statistics and quantify the age-specific mortality patterns associated with the 1918–1920 influenza pandemic in Japan, USA, and UK. All three countries showed highly elevated mortality risk in young adults relative to surrounding non-pandemic years. By contrast, the risk of death was low in the very young and very old. In Japan, the overall mortality impact was not limited to winter 1918–1919, and continued during winter 1919–1920. Mortality impact varied as much as threefold across the 47 Japanese prefectures, and differences in baseline mortality, population demographics, and density explained a small fraction of these variations. Our study highlights important geographical variations in timing and mortality impact of historical pandemics, in particular between the Eastern and Western hemispheres. In a future pandemic, vaccination in one region could save lives even months after the emergence of a pandemic virus in another region.
(Accepted January 07 2009)
(Online publication February 12 2009)