How the Spanish flu spread—and why the second wave was worse

“Their death was gruesome. They were coughing, racked by pain, high fevers. Some of them were bleeding from their eyes, nose, mouth and ears,” explains author and historian Kenneth C Davis

“And some of them were turning blue because they weren’t getting enough oxygen. In fact, before this was called the Spanish flu, it was called the Purple Death,” he said.

As the First World War drew to a close in 1918, the catastrophic Spanish flu epidemic erupted across the globe. But it was the second wave that was the worst.

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The flu killed anywhere between 50 million and 100 million people—and infected around a third of the world’s population.

It was March 1918 when the disease first appeared at an army base in Kansas, US. By the end of the month 38 soldiers had died and 1,100 people had been hospitalised.

This deadly virus spread quickly as troops were cramped together in trenches and barracks, and moved across borders.

Mass deployment of troops means that the infection was quickly spread as far afield as Boston in the US, Brest in France and Freetown in Sierra Leone.

“The rapid movement of soldiers around the globe was a major spreader of the disease,” said James Harris, a historian in infectious disease and the First World War.

“The entire military industrial complex of moving lots of men and material in crowded conditions was certainly a huge contributing factor in the ways the pandemic spread.”

The first rush of infections slowed to a halt in August. But it was followed by a second wave even more devastating than the last.

It was between September and November that year that Spanish flu really began to bite. The month of October 1918 saw 195,000 people die in the US alone.

Doctors puzzled over how quickly young and healthy people were dying.

“There were rows of corpses, absolutely rows of them, hundreds of them, dying from something quite different,” said Captain Geoffrey Keynes from the Royal Army Medical Corps.

“It was a ghastly sight to see, to see them lying there dead of something I didn’t have the treatment for.”

Mortality rates took the form of a “W curve”. There were high levels of deaths in the very young and very old—and a spike in otherwise healthy 25-35 year olds.

This may be because patients in that age group were exposed to the 1889-1890 Russian pandemic—which could have been similar to Spanish flu.

So it’s possible the middle spike in the W curve was because young and healthy people were overproducing the immune cells needed to fight the disease.

And the virus could have genetically mutated or merged with another type of virus or make it deadlier than the first.

Governments didn’t want to impose quarantines during wartime—despite public health officials understanding the risks of spreading infection.

For instance, the British state thought that, “the relentless needs of warfare justified incurring the risk of spreading infection,” argues Harris.

And in the US, a severe nursing shortage led to more deaths. That problem was compounded by the American Red Cross’s refusal to employ black nurses until the end of the pandemic.

Without the medical technology or scientific knowledge to produce a vaccine, a third wave broke out in Australia in January 1919. Once again it swept throughout the US and Europe.

But without the mass movement of troops, the infection wasn’t able to spread as quickly.

Davis argues that some form of social distancing helped to “flatten the curve” over a century ago—and argues a similar approach needs to be maintained today.

“It’s a very important lesson to learn that if we go too soon towards releasing those measures, it can be very, very costly. It certainly was in 1918.”