Was second wave of Spanish flu worse? Did it kill at least 20 million people?
The claim: The second wave of the Spanish flu reportedly killed 20 million to 50 million people after the first wave killed 3 million to 5 million people
A Facebook post claiming the second wave of the Spanish flu killed significantly more people than the first has garnered the attention of a public worried by the potential future of COVID-19.
The post, which more than 46,000 people have shared, reads: “People are so ready to get back to life forgetting that in 1918 the second wave of the Spanish flu reportedly killed 20-50 million. The first wave only killed 3-5 million. History does indeed repeat.”
USA TODAY reached out to the author of the post with a request for comment but did not receive a response.
The conversation surrounding the influenza pandemic of a century ago is not unique to social media users. Experts have drawn similar comparisons between the two pandemics in an attempt to better contextualize and understand the COVID-19 crisis.
But many of these comparisons fail to emphasize the more stark realities of the 1918 pandemic. Less-advanced health care systems and medical technology, the lack of an intergovernmental world health agency and an ongoing world war contributed to it becoming known as the worst pandemic in human history.
Fact check: Why is the 1918 influenza virus called ‘Spanish flu’?
An uncertain death count
Researchers have continued to investigate the Spanish flu. Its exact death toll and case fatality rate — the total number of deaths out of the total number of recorded cases —are unknown because of incomplete and inaccurate records in some less-developed regions.
“In 1918, death certificate recording and epidemiology was really in its infancy,” Amesh Adalja, a senior scholar at the Johns Hopkins Center for Health Security, explained in a recent NPR article. “We didn’t have all of that data. And there were many parts of the world that were not connected to other parts of the world. So you weren’t able to get data from some of the resource-poor areas that existed at that time.”
Alex Navarro is the assistant director of the Center for the History of Medicine at the University of Michigan. He’s researched the effects of the 1918 and 2009 influenza pandemics for more than a decade. Despite the presence of death records in the United States, “It’s really just a guess,” he said.
Navarro said influenza was not a reportable disease at the start of the 1918 pandemic, so it was difficult to know whether a person died of pneumonia or pneumonia caused by influenza.
Estimates range between 17.4 million and 100 million deaths worldwide.
Those figures come from a series of studies, including a 2018 study in the American Journal of Epidemiology, a 2002 study published in the John Hopkins University Press and a 1991 study from the Bulletin of the History of Medicine.
“What data there are tend to be inconsistent and of questionable validity, accuracy and robustness,” the 2002 study reads.
The claim about the Spanish flu happening in multiple waves is correct, although the number of waves is still subject to debate. The U.S. Centers for Disease Control and Prevention shows three waves on its website, although Navarro said “there’s generally considered to be four waves.”
These waves started in March 1918 and ended in the summer 1919, according to the CDC. Some believe a fourth wave happened in select regions in 1920.
It is true that the majority of U.S. deaths occurred during the fall 1918, the second wave of the pandemic, although exact death counts for each wave are unknown. The CDC calculated about 675,000 total deaths in the United States. Of those, about 195,000 happened during the second wave in October of 1918. That is roughly 28% of all U.S. deaths.
Experts state the second wave was more severe because of genetic mutation, wartime movement and because it was “more likely to be accompanied by bacterial pneumonias,” per the 1991 study.
Experts are still debating the Spanish flu’s case fatality rate.
A 2006 CDC article says the Spanish flu’s case fatality rate was around 2.5%, which would mean 2.5% of people infected died. But as science writer Ferris Jabr pointed out recently in Wired, the 2.5% figure is likely not accurate.
Many experts say 2.5% is too low. And the figures many media outlets and academics frequently reference — 2.5% case fatality rate, 500 million infected people, 50 million to 100 million deaths — are contradicting.
“If the Spanish flu infected 500 million and killed 50 to 100 million, the global CFR (case fatality rate) was 10 to 20 percent. If the fatality rate was in fact 2.5 percent, and if 500 million were infected, then the death toll was 12.5 million,” Jabr said in the Wired article. “There were 1.8 billion people in 1918. To make 50 million deaths compatible with a 2.5 percent CFR would require at least 2 billion infections — more than the number of people that existed at the time.”
The Facebook claim considers total deaths, not the case fatality rate, although the case fatality rate is unknown in part because experts don’t have an exact understanding of the Spanish flu’s mortality.
Because of the absence of complete and accurate records on the number of deaths during the Spanish flu pandemic and a lack of consensus on the length and number of the waves, it’s impossible to know how many people died during each.
For comparison to the war raging at the time, World War I had 8.5 million casualties among armed forces. It is estimated there were at least 13 million civilian casualties, though that is uncertain.
Our ruling: Partly false
We rate this claim to be PARTLY FALSE. Experts agree the Spanish flu occurred in multiple waves and that the second wave was significantly more deadly than the others. But it is false to attribute a specific number of deaths to each wave. Because of the lack of comprehensive medical records from 1918-20, there is not enough evidence to conclude an accurate number of deaths in any of the waves of the pandemic. Further, the CDC estimates 50 million people died overall in the pandemic, not just in the second wave.
Our fact-check sources
Facebook post, April 17, 2020
The Center for Infectious Disease Research and Policy
The Atlantic, The Coronavirus Is No 1918 Pandemic
American Journal of Epidemiology, Reassessing the Global Mortality Burden of the 1918 Influenza Pandemic
NPR, The 1918 Flu Pandemic Was Brutal, Killing More Than 50 Million People Worldwide
John Hopkins University Press, Updating the Accounts: Global Mortality of the 1918-1920 “Spanish” Influenza Pandemic
U.S. Centers for Disease Control and Prevention, 1918 Pandemic Influenza: Three Waves
U.S. Centers for Disease Control and Prevention, 1918 Pandemic Influenza Historic Timeline
Bulletin of the History of Medicine, The Geography and Mortality of the 1918 Influenza Pandemic
Emerging Infectious Diseases, 1918 Influenza: the Mother of All Pandemics
Wired, Covid-19 is Not the Spanish Flu
Interview with Alex Navarro, assistant director, Center for the History of Medicine at the University of Michigan, April 24, 2020
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This article originally appeared on USA TODAY: Fact check: Total deaths in each Spanish flu wave is unknown