Researchers say their findings "suggest that the mortality associated with COVID-19 during the early phase of the New York City outbreak was comparable to the peak mortality observed during the 1918 H1N1 influenza pandemic."
How does the lethality of COVID-19 compare with that of the Influenza pandemic of 1918?
In a study this week in JAMA Network, researchers at Harvard Medical School tried to find out by comparing estimated excess deaths in New York City during the first two months of the COVID-19 pandemic this spring and the peak of the Influenza 1918 pandemic.
The 1918 Influenza killed about 50 million people across the world, including 675,000 people in the United States.
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The Harvard study found that, during the peak of the 1918 H1N1 influenza outbreak in New York City, between October and November 1918, a total of 31, 589 all-cause deaths occurred among 5.5 million residents, yielding an incident rate of 287.17 deaths per 100,000 population.
The incident rate ratio for all-cause mortality during the H1N1 pandemic when compared with similar two-month spans from 1914 to 1917 was 2.80.
From March through May 2020 the COVID-19 outbreak in New York City saw 33,465 all-cause deaths occurred among 8.3 million residents, yielding an incident rate of 202.08 deaths per 100 000 population.
The incident rate ratio for all-cause mortality during the study period of 2020 compared with corresponding periods from 2017 through 2019 was 4.15.
In other words, the absolute increase in deaths over baseline during the peak of 1918 H1N1 influenza pandemic was higher than that observed during the first two months of the COVID-19 outbreak in New York City.
Nonetheless, the researchers said their findings "suggest that the mortality associated with COVID-19 during the early phase of the New York City outbreak was comparable to the peak mortality observed during the 1918 H1N1 influenza pandemic."
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The estimates came with caveats.
Notably, the baseline mortality rates from 2017 to 2019 were less than half that observed from 1914 to 1917, thanks to improvements in hygiene and advancements in medicine, public health, and safety.
As a result, the relative increase during early COVID-19 period was substantially greater than during the peak of the 1918 H1N1 influenza pandemic.
The study also could not directly compare the "native virulence" of the 1918 H1N1 influenza strain and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2).
And, it's not clear how many deaths from SARS-CoV-2 infection have been prevented because of modern interventions not widely available a century ago, including standard resuscitation, supplemental oxygen, mechanical ventilation, kidney replacement therapy, and extracorporeal membrane oxygenation.
"If insufficiently treated, SARS-CoV-2 infection may have comparable or greater mortality than 1918 H1N1 influenza virus infection," the researchers said.
“The mortality associated with COVID-19 during the early phase of the New York City outbreak was comparable to the peak mortality observed during the 1918 H1N1 influenza pandemic.”
Jeremy Samuel Faust, MD, Zhenqiu Lin, PhD; Carlos del Rio, MD
John Commins is a content specialist and online news editor for HealthLeaders, a Simplify Compliance brand.
KEY TAKEAWAYS
The absolute increase in deaths over baseline during the peak of 1918 H1N1 influenza pandemic was higher but "comparable" to that observed during the first two months of the COVID-19 outbreak.
The study could not directly compare the "native virulence" of the 1918 H1N1 influenza strain and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2).
It's not clear how many deaths from SARS-CoV-2 infection have been prevented because of modern interventions not widely available a century ago.