Did mutation ramp up the 1918 flu pandemic?

Why was fall outbreak deadlier than spring?

BOSTON — When it comes to deaths, COVID-19 still has a ways to go to catch up to the Influenza Pandemic of 1918-1919. The CDC estimates about 675,000 Americans died when that novel H1N1 virus swept across the globe; its transmission aided, in part, by the movement of troops involved in World War I.

So far, COVID-19 has killed about 375,000 Americans, the CDC reports. And it’s possible the surge in cases and, therefore, deaths in recent months could be due to the previously unknown presence of the more contagious British variant.

“At a given moment, more and more people will become infected,” said Dr. Brooke Nichols, an epidemiologist at the Boston University School of Public Health. “So even if it’s not killing more people, you know, [if] it’s not more severe, more people are likely to have it.”

In 1918, something similar may have happened. In March of that year, the United States experienced the first outbreaks of what would become known as The Spanish Flu – an erroneous term adopted because the press in neutral Spain escaped wartime censorship and freely wrote about the illness; that gave others the impression the flu came from there.

“It caused a great deal of sickness but it didn’t seem to cause a great deal of death,” said Dr. J. Alex Navarro, the assistant director of The Center for the History of Medicine at the University of Michigan. “Of course we know there was a deadly fall wave in 1918. And so the question is what happened between those two? Were they in fact the same strain of influenza? Was it something else?”

That is a medical mystery that has not been definitively solved, but not for lack of effort.

While some scientific papers have suggested the virus mutated from spring to fall, becoming more virulent, that has not been proven, Navarro said. In fact, a government research team compared tissue samples from the fall and spring waves but could not reach any conclusions.

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“There were some changes on the surface proteins to allow better binding,” Dr. Navarro said. “That alone, they speculate, would not likely account for why the fall wave was so much more deadly.”

Navarro said it’s also possible many of those who died contracted a secondary infection, such as bacterial pneumonia.

Still, research nearly 100 years after the 1918 pandemic indicates the virus could do plenty of damage on its own. In animal experiments, CDC researchers found a ‘reconstructed’ form of the virus to be exquisitely deadly, at least 100 times more lethal, for example, when compared with a modern flu virus.

Part of the virus’s power may be tied to an extremely high replication rate and the fact it concentrates on damaging just one human organ: the lungs.

In any case, Navarro said the clinical course of illness that fall of 1918 could be devastatingly quick.

“By early afternoon, they were starting to cough, not feel as well and run a fever,” he said. “And by later that night they were coughing their lungs out, basically…and dead overnight or the next day.”

One main difference between that pandemic and this one, Navarro said, is time. By the summer of 1919, the third, and what many consider the final, wave of the influenza pandemic was over – though cases continued to pop up in 1920.

It seems likely, given the high-transmission rate of COVID-19 and the possible lack of accessibility to vaccines in some parts of the world, that COVID-19 will be a presence for much longer.

One similarity between the two pandemics, Navarro said, is that Americans grew tired back then of restrictions, just as they did this past fall.

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“The result is that we’re going through this really terrible third surge,” he said. “We have the big hammer of closures, but when those don’t work anymore because people aren’t following them or when there’s not the political will to reenact them strictly, this is what we’re going to go through.

“I really fear that we’re experiencing the same thing that we went through at the end of the fall wave and early winter wave of 1918/1919, which is people just become inured to death and they just go about their lives as if the pandemic didn’t really exist,” he added.

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