Hypotheses about the source
United Kingdom
The major UK troop staging and hospital camp in
Étaples in France has been theorized by researchers as being at the center of the Spanish flu. The research was published in 1999 by a British team, led by
virologist John Oxford.
[17] In late 1917, military pathologists reported the onset of a new disease with high mortality that they later recognized as the flu. The overcrowded camp and hospital was an ideal site for the spreading of a respiratory virus. The hospital treated thousands of victims of chemical attacks, and other casualties of war, and 100,000 soldiers passed through the camp every day. It also was home to a
piggery, and
poultry was regularly brought in for food supplies from surrounding villages. Oxford and his team postulated that a significant precursor virus, harbored in birds,
mutated and then migrated to pigs kept near the front.
[18][19]
A report published in 2016 in the Journal of the
Chinese Medical Association found evidence that the 1918 virus had been circulating in the European armies for months and possibly years before the 1918 pandemic.
[20]
United States
There have been statements that the epidemic originated in the United States. Historian
Alfred W. Crosby stated in 2003 that the flu originated in
Kansas,
[21] and popular author
John Barry described
Haskell County, Kansas, as the point of origin in his 2004 article.
[11] It has also been stated by historian Santiago Mata in 2017 that, by late 1917, there had already been a first wave of the epidemic in at least 14 US military camps.
[22]
A 2018 study of tissue slides and medical reports led by evolutionary biology professor Michael Worobey found evidence against the disease originating from Kansas as those cases were milder and had fewer deaths compared to the situation in New York City in the same time period. The study did find evidence through
phylogenetic analyses that the virus likely had a North American origin, though it was not conclusive. In addition, the
haemagglutinin glycoproteins of the virus suggest that it was around far prior to 1918 and other studies suggest that the
reassortment of the H1N1 virus likely occurred in or around 1915.
[23]
China
One of the few regions of the world seemingly less affected by the 1918 flu pandemic was
China, where there may have been a comparatively mild flu season in 1918 (although this is disputed due to lack of data during the
Warlord Period of China, see
Around the globe). Multiple studies have documented that there were relatively few deaths from the flu in China compared to other regions of the world.
[24][25][26] This has led to speculation that the 1918 flu pandemic originated in China.
[27][25][28][29] The relatively mild flu season and lower rates of flu mortality in China in 1918 may be explained due to the fact that the Chinese population had already possessed
acquired immunity to the flu virus.
[30][27][25] However, a study by K.F. Cheng and P.C. Leung in 2006 has suggested it was more likely because the traditional Chinese medicine played an important role in prevention and treatment.
[27]
In 1993, Claude Hannoun, the leading expert on the 1918 flu for the
Pasteur Institute, asserted the former virus was likely to have come from China. It then mutated in the United States near
Boston and from there spread to
Brest,
France, Europe's battlefields, Europe, and the world with
Allied soldiers and sailors as the main disseminators.
[31] He considered several other hypotheses of origin, such as Spain, Kansas and Brest, as being possible, but not likely. Political scientist
Andrew Price-Smith published data from the
Austrian archives suggesting the influenza had earlier origins, beginning in Austria in early 1917.
[32]
In 2014, historian Mark Humphries argued that the mobilization of 96,000
Chinese laborers to work behind the British and French lines might have been the source of the pandemic. Humphries, of the
Memorial University of Newfoundland in
St. John's, based his conclusions on newly unearthed records. He found archival evidence that a respiratory illness that struck northern China in November 1917 was identified a year later by Chinese health officials as identical to the Spanish flu.
[33][34]
A report published in 2016 in the Journal of the
Chinese Medical Association found no evidence that the 1918 virus was imported to Europe via Chinese and Southeast Asian soldiers and workers and instead found evidence of its circulation in Europe before the pandemic.
[20] The 2016 study suggested that the low flu mortality rate (an estimated 1/1000) found among the Chinese and Southeast Asian workers in Europe meant that the deadly 1918 influenza pandemic could not have originated from those workers.
[20]
A 2018 study of tissue slides and medical reports led by evolutionary biology professor Michael Worobey found evidence against the disease being spread by Chinese workers, noting that workers entered Europe through other routes that did not result in detectable spread, making them unlikely to have been the original hosts.
[23]
