The 1918 influenza pandemic is the deadliest in modern history, claiming an estimated 50 million lives worldwide, including 675,000 in the United States.

By some measures, the toll of the Covid-19 surge in New York City this spring resembled that of the 1918 flu pandemic.

In March and April, the overall death rate was just 30 percent lower than during the height of the pandemic in the city, despite modern medical advances, according to an analysis published on Thursday in JAMA Network Open.

Many people liken Covid-19 to seasonal influenza while regarding the 1918 flu pandemic as a time of incomparable devastation, said Dr.

Faust and his colleagues compared data for “all-cause mortality” — deaths from any cause — in New York City during two pandemic periods.

Nearly 33,500 people died in New York City between March 11 and May 11 of this year, according to the city’s Department of Health and Mental Hygiene.

The researchers then looked at deaths in October and November of 1918, the peak of the city’s flu outbreak.

Faust identified 31,589 deaths among 5.5 million city residents, for an incident rate of 287.17 deaths per 100,000 person-months.

In all, the death rate in the city last spring was about 70 percent of that seen in 1918.

When the epidemic hit in 1918, the spike in deaths was not as shocking to the city as it was in 2020.

Given the enormous leaps in medicine over the past century, the similarity in death rates today and in 1918 is particularly disconcerting, she and other experts said.

The New York City Department of Health’s data for 1918 would have enabled the researchers to include deaths from September 15, the start of the peak — “a better time period,” said J