Mortality From 1918-1919 Spanish Flu Among the American Expeditionary Forces Analyzed Through People-Powered Research

The Card Register of Burials of Deceased American Soldiers, 1917-1922 holds the burial cards of American servicemen and women who died at sea or overseas during or after World War I (WWI). We aimed to use this online register to study mortality statistics in the American Expeditionary Forces (AEF) during the 3 waves of Spanish flu in 1918 and 1919. However, the register, which includes 104 file units, lacks database query functionality.

Over 6,000 volunteers attached to the Zooniverse platform for people-powered research submitted 4 million transcription tasks from individual burial cards in the online register. This information was used to create the American WWI Burial Cards Search Tool, which is a free online searchable database that also allows, among others, for study of mortality statistics.

The first wave of Spanish flu resulted in a relevant increase in mortality in the AEF. During the second wave, mortality increased significantly, peaking on October 9, 1918, with 474 deaths. Moreover, data show that the weekly mortality rate started to increase already in early August, in contrast to a previous report stating that the second wave of Spanish flu ran its course in the AEF roughly from September 15 onwards. In all, at least 14,494 servicepersons in the AEF died from influenza and/or pneumonia during the deadly second and third waves of Spanish flu. In contrast, mortality from COVID-19 in the U.S. military was low, with 96 deaths as of December 8, 2022.

People-powered research provided a unique possibility to study single-day mortality figures from influenza and/or pneumonia in the AEF during the different waves of Spanish flu. In all, at least 14,494 servicepersons in the AEF died from influenza and/or pneumonia during the second and third waves of Spanish flu, while we show that the weekly mortality rate during the second wave increased already in early August 1918. In contrast, mortality from COVID-19 in the U.S. military was low. Thus, pandemics of respiratory infections have different impacts on mortality in army personnel, depending on specific pathogenic characteristics of the causative agent.