Source: By Otis Historical Archives, National Museum of Health and Medicine - Emergency hospital during influenza epidemic (NCP 1603), National Museum of Health and Medicine.https://www.buckscountycouriertimes.com/news/20190923/mxfctter-museum-to-mark-historic-influenza-pandemic/1, Public Domain, https://commons.wikimedia.org/w/index.php?curid=25513204
History of 1918 flu pandemic | CDC
The 1918 influenza pandemic was the most severe pandemic in recent history. It was caused by an H1N1 virus with genes of avian origin. Although there is not universal consensus regarding where the virus originated, it spread worldwide during 1918-1919. In the United States, it was first identified in military personnel in spring 1918.