Sealed Railcars
At the time of the outbreak, British and French officials were forming the Chinese Labor Corps, which eventually shipped some 94,000 laborers from northern China to southern England and France during the war.
"The idea was to free up soldiers to head to the front at a time when they were desperate for manpower," Humphries says.
Shipping the laborers around Africa was too time-consuming and tied up too much shipping, so British officials turned to shipping the laborers to Vancouver on the Canadian West Coast and sending them by train to Halifax on the East Coast, from which they could be sent to Europe.
So desperate was the need for labor that on March 2, 1918, a ship loaded with 1,899 Chinese Labor Corps men left the Chinese port of Wehaiwei for Vancouver despite "plague" stopping the recruiting for workers there.
In reaction to anti-Chinese feelings rife in western Canada at the time, the trains that carried the workers from Vancouver were sealed, Humphries says. Special Railway Service Guards watched the laborers, who were kept in camps surrounded by barbed wire. Newspapers were banned from reporting on their movement.
Roughly 3,000 of the workers ended up in medical quarantine, their illnesses often blamed on their "lazy" natures by Canadian doctors, Humphries said: "They had very stereotypical, racist views of the Chinese."
Doctors treated sore throats with castor oil and sent the Chinese back to their camps.
The Chinese laborers arrived in southern England by January 1918 and were sent to France, where the Chinese Hospital at Noyelles-sur-Mer recorded hundreds of their deaths from respiratory illness.
Historians have suggested that the Spanish influenza mutated and became most deadly in spring 1918, spreading from Europe to ports as far apart as Boston and Freetown, Sierra Leone.
By the height of the global pandemic that autumn, however, no more such cases were reported among the Chinese laborers in Europe.
Medical Evidence
Humphries concedes that a final answer to the mystery of the Spanish flu's origins is still a ways off.
"What we really need is a sample of the virus preserved in a burial for the medical experts to uncover," Humphries says. "That would have the best chances of settling the debate."
For the last decade, experts such as Jeffery Taubenberger, of the National Institute of Allergy and Infectious Diseases, have sought burial samples across continents, seeking to find preserved samples of the virus in victims of the outbreak.
Taubenberger led a team in 2011 that looked at flu virus samples taken from autopsies of 32 victims of the 1918 outbreak.
The earliest sample found so far was from a U.S. soldier who died on May 11, 1918, at Camp Dodge, Iowa, but the team is looking for earlier cases.
A broad number of samples from flu victims before and after the pandemic might finally narrow down its origins. Essentially, scientists would need a genetically identified sample of the influenza's H1N1 virus taken from a victim who died before the first widespread outbreak of the pandemic in spring 1918 to point to a time and place as the likely origin point of the pandemic.
One from China in 1917, for example, would fill the bill.
"I'm not sure if this question can ever be fully answered," Taubenberger cautions, noting that even the origin of a smaller flu pandemic in 2009 still eludes certainty.
Ultimately, "these kinds of [historical] analyses cannot definitively reveal the origins and patterns of spread of emerging pathogens, especially at the early stages of the outbreak," Taubenberger said, of the new historical report.
In the end, however, knowing the origin of the disease might provide information that could help stop a future pandemic, making the search worthwhile.
"I would say that the takeaway message of all of this is to keep your eye on China" as a source of emerging diseases, Higgins says. He points to concerns about avian flu and the SARS virus, both arising from Asia in the last decade.
The SARS outbreak claimed perhaps 775 lives in 2003, and avian flu A (H5N1) has killed 384 people since 2003, according to the World Health Organization, which is carefully watching for signs of an outbreak of the diseases.
"We have seen a lot of emerging diseases travel around the world in recent decades," Higgins says.
History has a way of repeating, he says, and research into the origins of the 1918 flu could help prevent a scourge like that from happening again.
Editor's Note: This story has been updated to correct the location of Camp Dodge.
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