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Deaths during the coronavirus surge in New York City recall the peak of the 1918 flu pandemic

(CNN) A new study finds that deaths in New York City in the early part of the Covid-19 pandemic were comparable to deaths in the city at the peak of what's considered the deadliest pandemic to date -- the flu pandemic of 1918.

The relative increase in deaths during the early period of the Covid-19 pandemic was actually substantially greater than during the peak of the 1918 pandemic, according to the study published Thursday in JAMA Network Open.

"The big takeaway is that when we compare what happened, we find that the magnitude of change in deaths -- like how big a shock to the system this is -- these pandemics are very similar," said study co-author Dr. Jeremy Faust, an emergency physician at Brigham and Women's Hospital and is an instructor at Harvard Medical School. "In fact, if you think about it, Covid-19's a bigger shock to our health care system today because we have usually just a lower death rate than we did in 1918. So Covid-19 is a bigger change from norms for us than the 1918 flu was."

Faust said by comparing the first two months of the pandemic in New York to the worst two months of the pandemic in New York 100 years ago, the Covid-19 period had over 70% as many deaths per capita.

"Who knows what would be the case if we didn't have modern ICUs and we couldn't treat secondary infections with antibiotics or put people on ventilators or had oxygen," Faust said. "If you compare these viruses side by side, without all the medical bells and whistles we have today, I'd say Covid-19 is worse."

"We'll never know that for sure, because thankfully now we have the ability to save more lives, but even with all our technology and medical progress, the death rate being 70% as bad as it was at the worst point in 1918, I think people don't realize how serious this is," Faust said.

Faust said some people may underestimate how bad this pandemic is, because they are picturing a historic pandemic or plague, like something out of a movie where the cart pulls over on the side of the road and picks up bodies.

"That's what those refrigerated trucks outside of the hospital are, by the way," Faust said.

The 1918 flu is estimated to have infected a third of the world's population and caused approximately 50 million deaths. Like with this pandemic, it impacted some communities more than others.

This study only takes into account data that is specific to New York City. It cannot be used to characterize the extent of this pandemic in other cities or nationwide. New York was hit hard early in the pandemic, and since then, other cities have learned from what worked early on, experts said.

John Barry, the author of the 2004 book "The Great Influenza," said he found the study results surprising.

Barry, who was not involved in the new study, said from other indicators he thinks its clear that the 1918 pandemic was "considerably more virulent" than the Covid-19 pandemic, at least for the country.

"I guess when New York was hit we didn't really know how to handle cases yet. Since then we've learned a lot more," Barry said. "I think New York's death toll from Covid-19 is probably higher ... and that will be cut down after that first wave of exposure, but even still, I was surprised that there is no greater difference in these numbers."

In terms of deaths, New York had it better than many other cities in 1918, Barry said. The city was exposed to the virus in spring and saw 33,000 deaths over the course of the pandemic, which was a small number compared to some other cities.

Barry also said with the Covid-19 pandemic, doctors have more options to care for patients. There is no cure, but even the supportive care doctors provide patients now is much better than what patients had in 1918.

"In 1918, supportive care was non-existent," Barry said.

Faust said what he most wants people to take away from this study is the understanding of exactly how serious this pandemic is.

"We don't need to wait until the end of it to look back and see that these events are similar in magnitude," Faust said. "What I am driving home here is, that if we don't do something, if we don't take this really seriously, we very much a year from now, could be looking at those same numbers we saw from 1918."