CDC study: It's possible that only 1 in 8 US infections have been counted

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https://www.cnn.com/2020/11/26/health/us-coronavirus-thursday/index.html 

CDC study: It's possible that only 1 in 8 US infections have been counted

Only about 1 in 8 -- or 13% -- of all coronavirus infections in the United States were recognized and reported through the end of September, a new modeling study suggests.

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That estimate, made by researchers at the US Centers for Disease Control and Prevention, would mean that as many as 53 million people in the United States could have been infected from February through September.

During that same period, around 7 million confirmed cases of symptomatic Covid-19 were reported nationally, the researchers said.

As of Thursday, health authorities have identified more than 12.8 million Covid-19 cases total in the United States so far, according to Johns Hopkins University.

"We estimated that in the US through September 30, 2020, there were approximately 53 million total SARS-CoV-2 infections, including 42 million symptomatic illnesses and 2.4 million hospitalizations, with large variations by age group and geographic area," the CDC researchers wrote in the study published in the journal Clinical Infectious Diseases on Wednesday.

Fifty-three million would be about 16% of the US population of 330.6 million.

To estimate the number of Covid-19 cases that might have been missed since the beginning of the pandemic, the researchers used a model to adjust the reported numbers of symptomatic cases in the United States. They considered what's known about detecting cases, asymptomatic cases, patients seeking care or not and the risk of false negative test results.

Their study had some limitations, including that the availability and use of testing has changed over time, and their findings are based on a probabilistic model -- so they serve only as estimates.

Researchers have been reporting for months that official case tallies have likely been vast undercounts, especially early in the pandemic, partly because of limited test availability.

Overall, while the numbers of Covid-19 cases in the study may seem large, the researchers emphasized that 84% of the US population would not have been infected by the end of September, and that therefore "most of the country remains at risk, despite already high rates of hospitalization."

CNN's Ray Sanchez, Pete Muntean, Ben Tinker, Jacqueline Howard, Shelby Lin Erdman and Naomi Thomas contributed to this report.