The number of people infected with the coronavirus in different parts of the United States was anywhere from two to 13 times higher than the reported rates for those regions, according to data released Tuesday by the Centers for Disease Control and Prevention.
The findings suggest that large numbers of people who did not have symptoms or did not seek medical care may have kept the virus circulating in their communities. The study is the largest of its kind to date, although some early data was released last month.
“These data continue to show that the number of people who have been infected with the virus that causes Covid-19 far exceeds the number of reported cases,” Dr. Fiona Havers, the C.D.C. researcher who led the study, said in an email. “Many of these people likely had no symptoms or mild illness and may have had no idea that they were infected.”
The researchers analyzed samples from people who had routine clinical tests, or were inpatients at hospitals, in 10 cities and states for evidence of prior virus infection. The team released early data for six of the sites in June, and for all 10 locations Tuesday in the journal JAMA. They also released data from later times for eight sites to the C.D.C.’s website on Tuesday.
About 40 percent of infected people do not develop symptoms, but they may still pass the virus on to others.
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Text of CDC study on coronavirus cases