The estimate comes from a nationwide look at antibody tests.

A bar in the East Village of New York on June 12.Jeenah Moon / Reuters

The true number of Americans who’ve been infected with COVID-19 may top 20 million, according to new estimates from the Centers for Disease Control and Prevention.

“Our best estimate right now is that for every case that’s reported, there actually are 10 other infections,” Dr. Robert Redfield, director of the CDC, said on a call with reporters Thursday.

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The assessment comes from looking at blood samples across the country for the presence of antibodies to the virus. For every confirmed case of COVID-19, 10 more people had antibodies, Redfield said, referring to proteins in the blood that indicate whether a person’s immune system has previously fought off the coronavirus.

Those samples aren’t just from people who have had antibody testing. They also come from testing performed on donated blood at blood banks or from other laboratory testing of blood.

Currently, there are 2.3 million COVID-19 cases reported in the U.S. The CDC’s new estimate pushes the actual number of coronavirus cases up to at least 23 million.

“This virus causes so much asymptomatic infection,” Redfield said. “The traditional approach of looking for symptomatic illness and diagnosing it obviously underestimates the total amount of infections.”

The estimation comes amid rises in cases across the Southeast and Western U.S., particularly among younger adults in their 20s, 30s and 40s.

Also Thursday, the CDC expanded its list of who is at greatest risk for COVID-19 complications, removing the age cutoff of 65.

“There’s not an exact cutoff of age at which people should or should not be concerned,” Dr. Jay Butler, head of the COVID-19 response at the CDC, said. Rather, a person’s risk increases with age, but that doesn’t preclude younger adults from complications.

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