Both came from china.
In 1993, Claude Hannoun, the leading expert on the Spanish flu at the
Pasteur Institute, asserted the precursor virus was likely to have come from
China and then mutated in the United States near
Boston and from there spread to
Brest,
France, Europe's battlefields, the rest of Europe, and the rest of the world, with
Allied soldiers and sailors as the main disseminators.
[129] Hannoun considered several alternative hypotheses of origin, such as Spain, Kansas, and Brest, as being possible, but not likely.
[129] 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 (where the laborers came from) in November 1917 was identified a year later by Chinese health officials as identical to the Spanish flu.
[130][131] However, no tissue samples have survived for modern comparison.
[132] Nevertheless, there were some reports of respiratory illness on parts of the path the laborers took to get to Europe, which also passed through North America.
[132]
China was one of the few regions of the world seemingly less affected by the Spanish flu pandemic, where several studies have documented a comparatively mild flu season in 1918.
[133][134][135] (Although this is disputed due to lack of data during the
Warlord Period, see
Around the globe.) This has led to speculation that the Spanish flu pandemic originated in China,
[135][136] as the lower rates of flu mortality may be explained by the Chinese population's previously
acquired immunity to the flu virus.
[137][135]