WWI 'Climate Anomaly' May Have Been Behind the Flu Epidemic

Who would've guessed an interplay of environmental, ecological, epidemiological, and human factors would be at play during the Great War.
Utku Kucukduner
U.S. Army Camp Hospital No. 45, Aix-Les-Bains, France, Influenza Ward No. 1.The National Museum of Health and Medicine

A new research focusing on the climate during the years of World War 1 and the influenza pandemic (often misnamed as 'the Spanish Flu') of the years 1918 and 1919 revealed a curious phenomenon. The researchers believe that climate anomalies along the Western Front in Europe that saw some unusual weather conditions, with torrents of rain, and crisp cold temperatures have amplified — or maybe even onset — the notorious flu pandemic.

The research led by the climate scientist and historian Alexander More is published in GeoHealth.


The onset hypothesis suggests that the exceptionally cold temperatures during the time have altered the migratory behavior of ducks, who are known to carry the H1N1 virus.

Soldiers deployed at the war riddled fronts in the west suffered greatly from the harsh environment at the time with incessant rains and unbearable cold, especially at the battles of Verdun, Somme, and Passchendaele.

Constant artillery fire turned natural landscapes into wastelands and the subsequent rains made these wretched lands into perilous mires. Soldiers often needed a hand from a fellow compatriot to unstuck themselves and not all of them found one. Canadian veteran George Peakes recalls, “many wounded men slipped into those shell holes and would have been drowned or suffocated by the clammy mud.”

Soldiers could not keep their feet dry and quality-of-life in the trenches pretty much sucked in general. Rashing frostbites and subsequent neuropathies and gangrenes were common.

Although your first guess might be that general low quality-of-life was what caused the pandemic to soar but it's something different.

The weather is not the only cause

To conduct their study, the team extracted ice core samples from the European Alps, with which they reconstructed the climate conditions from 1914 through 1919. Then, they compared their data to the mortality rates across Europe and the historical accounts of the aforementioned torrential rains. They found that winters of 1915, 1916, and 1918 were especially harsh.

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The paper reads: “The data presented here show that extreme weather anomalies captured in [ice cores] and reanalysis records brought unusually strong influxes of cold marine air from the North Atlantic, primarily between 1915 and 1919, resulting in unusually strong precipitation events, and that they exacerbated total mortality across Europe."

On top of this, the authors suggest the unusual weather conditions might have caused mallard ducks to stay instead of migrating to Russia as they typically would. Study notes that mallards are a flourishing harbor for the H1N1 avian flu. Since they hanged around civilian settlements, military encampments, they have had the chance to interact with domesticated animals more, and their fecal matter had a higher chance of finding its way into water sources. Remember the torrential rains, well, they most likely helped exacerbate the water contamination problem. 

Although authors note that this theory of ducks should be taken with a grain of salt as it's highly speculative.

It's still interesting how, in the authors' words “the interplay of environmental, ecological, epidemiological, and human factors,” resulted in exacerbation of this already problematic matter.


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