Hollywood renditions of global pandemics are particularly terrifying because of the subtext of possibility – after all, global pandemics have dotted human history and will likely recur. In the end, though, a scientist-hero usually cracks the code and humanity triumphs. In reality, many viral codes are left undeciphered. The Spanish Flu, which infected a quarter of the world’s population 100 years ago this year, is a riddle that remains largely unsolved.

The 1918 pandemic ended simply by running its course, without significant human intervention. Now, we know that it was the influenza virus that killed up to 100 million people, but we don’t know for certain where or how it began – making it harder to plan for a repeat disaster.

The statistics around the Spanish Flu are staggering. Within months it had already killed more than any other disease in human history – and the pandemic stretched on for years. The disease was little understood at the time, and accurate statistics are difficult to come by, but estimations of deaths range between 50 and 100 million, all within the span of about two years. In India alone, as many as 20 million perished. By comparison, the World Health Organization estimates that HIV has killed 35 million people in total since its inception. The disease was truly a global pandemic, sprouting up on three continents within a week and disrupting social order on a global scale.


Unnamed photographer for National Photo Company

Red Cross litter carriers transport a victim of Spanish Flu in Washington DC in 1918.

Unlike other influenza outbreaks, which tend to affect the very young and old, the Spanish Flu was most lethal for the healthy and robust, exactly those who were congregating from all over the world on the battlefields of Europe. The combined losses of those in their prime in the trenches and from the Spanish Flu led American man of letters Gertrude Stein to coin the “Lost Generation.” After the epidemic passed with no great human triumph, memories of its passage quietly faded from the popular conscious. It wasn’t something people wanted to dwell on.

While expanded virology research led to the discovery of the influenza virus in the '30s and initiation of vaccination campaigns in the '40s, fruitful efforts to understand the 1918 strand did not begin in earnest until the 1990s (with the epic exception of a University of Iowa graduate student who unearthed samples from permafrost-preserved Eskimos in 1951).

Using modern genetic analysis techniques, we have learned a lot about the nature of the Spanish Flu. For example, the entire eight-segment genome of the virus has now been sequenced, and we know that it was caused by the H1N1 subtype of the influenza A virus. Despite these advances, an important question remains: where did the virus come from?

Throughout history, many flu pandemics have originated in China. The influenza virus can incorporate the genetic material of animals, particularly swine and fowl, to evade the human immune system and wreak havoc. Experts postulate that the close proximity of large populations of humans and domestic animals in China creates an environment ripe for outbreak.

Indeed, media reports last year warned that the virus "most likely to cause the next flu pandemic", in this case H7N9 avian influenza, had so far only been detected in China.


Credit: Reuters/TPG

An health worker puts a dead chicken inside a trash bag at a wholesale poultry market in Hong Kong, 2014. Hong Kong began culling 20,000 chickens after the discovery of the H7N9 bird flu virus in a batch of live chicken from Guangdong.

Given these facts, for decades China – along with the American Midwest and Western Europe – has been on the shortlist for possible places that the 1918 pandemic originated. The China-origin theory received a huge boost in 2014 when a Canadian historian found that China experienced an outbreak of a pneumonia in 1917 that was similar to the Spanish Flu.

During the outbreak, Allied forces were recruiting Chinese laborers to help with the war effort in Europe. The theory goes that these 94,000 laborers, many of whom were supposedly infected, were transported across Canada via rail and finally to Europe, ensuring the global spread of the pandemic. At the time, this revelation was seen as “about as close to a smoking gun as a historian is going to get” showing that the influenza virus came from China.

But recent studies have further muddied the picture. In 2016, Dr. Dennis Shanks, Director of the Australian Defense Forces Malaria and Infectious Diseases Institute, published data showing that the Chinese laborers peak mortality rates from flu lagged rather than preceded the other nearby military camps. According to Shanks, if the Chinese laborers did incubate the virus, then one would expect that they would fall sick before, rather than after, their neighbors. Rather, he believes a preexisting virus in Europe underwent a genetic shift to become particularly lethal.

Shanks believes the China-origin theory is a “reasonable thing for discussion” based on the fact that China’s intimate animal domestication allows for viruses to mutate more quickly, but he also cautions against this type of linear thinking. “Blaming exterior sources for a virus is very common just because we almost intrinsically think that an awful disease must have come from somewhere else,” he said. “Particularly in our current transport system, we need to not think in those small categories but realize that genetic material is moving across the world rapidly all the time.” As an example, Shanks highlights that due to modern transportation, we have more exchange of genetic material on a daily basis than we did in 1918, even as the entire world was descending on the battlefields of Europe.

Of course, not knowing the origin makes it harder to plan for the future. Experts remain largely flummoxed by what conclusions to draw from the Spanish Flu. One hundred years later, this makes the Spanish Flu as relevant as ever to researchers. As one group of scientists wrote of the mystery surrounding the largest mortality event in human history, “We must continue to examine this long-ago tragedy, allowing it to stand clearly before us as a challenge to complacency, as a modern problem with future implications.”

Many are heeding this call, applying increasingly advanced techniques to examine samples from China and elsewhere. University of Arizona Professor of Ecology and Evolutionary Biology Michael Worobey is currently searching for tissue samples from China between 1900 to 1918. “You never know what hospitals have in their pathology collections until you start asking questions and poking around,” he told The News Lens in an email. If he found the presence of a matching H1N1 strain in a sample prior to 1918, that would truly constitute the “smoking gun” that could put the mystery to bed.

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Editor: David Green