For most of the past century, scientists and medical researchers have hotly debated the origins of the 1918 influenza outbreak. Although the pandemic had been dubbed the “Spanish flu,” it only appeared to hit harder in neutral Spain because the country was free from wartime newspaper censors such as those in the United States, France and the United Kingdom who minimized reports of the influenza outbreak in order to prevent potential panic. While some researchers have pointed to a military camp in Kansas or the front-line trenches in France as the breeding ground for the disease, a Canadian historian believes he has discovered evidence to support those who theorized that the “Spanish flu” actually started a world away in China.

According to a new article published in the January 2014 issue of the journal War in History, historian Mark Humphries of Canada’s Memorial University of Newfoundland points to newly unearthed records to make the case that the lethal influenza pandemic first appeared in China in 1917 and then exploded across the globe “as previously isolated populations came into contact with one another on the battlefields of Europe.”

Humphries, author of “The Last Plague: Spanish Influenza and the Politics of Public Health in Canada,” writes that victims of a mysterious respiratory disease that broke out in northern China in November 1917 suffered many of the same symptoms as those of the “Spanish flu.” Doctors reported that patients turned blue from a lack of oxygen, coughed up blood and suffered from fevers, headaches, pneumonia and shortness of breath. The highly contagious and deadly disease was particularly unusual in that it killed otherwise healthy adults between the ages of 18 and 40 by seemingly turning their strong immune systems against them. However, with no solid scientific evidence of the outbreak’s cause, local Chinese health officials labeled it “winter sickness” and chose not to quarantine citizens or enact travel restrictions.

How would have the influenza strain spread from China to North America and Europe? Humphries points to a historical footnote from World War I—the shipment of 94,000 laborers from northern China to southern England and France to free up able-bodied British and French citizens to fight on the front lines of the Western Front. During the winter of 1917, upwards of 20,000 workers a month from the plague-infected area of China arrived in the British-leased port city of Weihaiwei to become part of the Chinese Labor Corps. They were packed into crowded barracks, which were breeding grounds for influenza. Although the British were aware of the outbreaks at their barracks, they still shipped out the Chinese workers.

The Chinese Labor Corps was originally transported around Africa or by way of the Suez Canal, but as resources were diverted to troop transports, the British needed an alternative route to Europe. Canada gave its assent for the Chinese laborers to land in Vancouver, travel across the country by train and depart for Europe from the Atlantic port of Halifax. However, with nativist feelings running high in wartime Canada and fears that the Chinese laborers might attempt to escape inside their country, Canadian authorities kept the operation secret, banning coverage of it in the press and placing special army guards inside sealed train cars with the Chinese workers and stationing them at camps encased in barbed wire.

Humphries found medical records indicating that more than 3,000 of the 25,000 Chinese Labor Corps workers transported across Canada beginning in 1917 ended up in medical quarantine, many with flu-like symptoms. The influenza ripped through the Canadian guards and soon took root in North America. “Ethnocentric fears—both official and popular—facilitated its spread along military pathways that had been carved out across the globe to sustain the war effort on the Western Front,” Humphries write.

Hundreds of the Chinese who continued on to Europe died there of respiratory illness, and the influenza they brought with them “mutated and then exploded along the sinews of war,” according to the journal article. The flu outbreak that came from China boomeranged back to North America and then across the Pacific Ocean. This deadly wave, however, proved much less lethal in China than the mysterious illness that broke out in 1917, which Humphries points to as potential proof that it was the epicenter of the outbreak because it suggests “some immunity was at large in the population because of earlier exposure to the virus.”

The mystery of the origins of the “Spanish flu,” is not totally solved, however. “Only DNA testing of samples from these earlier outbreaks can truly confirm or deny the theory,” Humphries acknowledges.