Covid-19 is on track to kill far more people in the United States this year than the seasonal flu.
But determining just how deadly the new coronavirus will be is a key question facing epidemiologists, who expect resurgent waves of infection that could last into 2022.
As the virus spread across the world in late February and March, the projection circulated by infectious disease experts of how many infected people would die seemed plenty dire: around 1 percent, or 10 times the rate of a typical flu.
But according to various unofficial Covid-19 trackers that calculate the death rate by dividing total deaths by the number of known cases, about 6.4 percent of people infected with the virus have now died worldwide.
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The known number of coronavirus cases worldwide is about two million, and at least 127,000 of those patients have died. The United States has an estimated 600,000 reported cases and more than 25,000 deaths, the most in the world.
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What scientists call the infection fatality rate is so closely watched because even a seemingly trivial decrease — from, say, 1.0 percent to 0.9 percent — could mean a few hundred thousand fewer deaths in a population the size of the United States.
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Even as parts of the country edge toward reopening, cases are rising in Florida and other Southern states whose governors delayed closing beaches and dine-in restaurants. And it is the virus’s transmission rate, as much as its infection fatality rate, that is preoccupying public health experts trying to find a way forward.
“Everyone in the whole country is vulnerable to this,” said Andrew Noymer, an associate professor of public health at the University of California, Irvine. “Nobody has pre-immunity. That’s totally unlike flu. So New York had some early cases, it spread like crazy. But why is Des Moines not going to have a Covid epidemic? What’s so special about Springfield, Ill.? Social distancing will end. And people will start getting it again and dying.”