PATHS OF INFECTION: Map depicting the Spanish flu pandemic 1918, Patterson KD, Pyle GF, "The Geography and Mortality of the 1918 Influenza Pandemic." In a 2014 report, titled “Paths of Infection: The First World War and the Origins of the 1918 Influenza Pandemic,” (Source: https://bit.ly/2T7m39z) historian Mark Osborne Humphries claims he had 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. He also found medical records indicating that more than 3,000 of the 25,000 Chinese Labor Corps workers who were transported across Canada en route to Europe starting in 1917 ended up in medical quarantine, many with flu-like symptoms.
Bulletin of the History of Medicine, 1991; 65(1): 4-21.