Far more Americans have been infected with COVID-19 than reported case counts reflect, a new government report suggests.
COVID-19 infections were anywhere from six to 24 times higher than the number of reported cases in 10 different sites across the United States tested at different times during the pandemic, the U.S. Centers for Disease Control and Prevention study found.
In seven U.S. locales, there were more than 10 times the number of COVID-19 infections than there were reported cases, antibody testing led by Dr. Fiona Havers, of the CDC's COVID-19 Response Team, revealed.
"The findings may reflect the number of persons who had mild or no illness or who did not seek medical care or undergo testing but who still may have contributed to ongoing virus transmission in the population," the researchers concluded.
The findings were published July 21 in the journal JAMA Internal Medicine.
The percentage of people with COVID-19 coronavirus antibodies in their blood ranged from 1% in the San Francisco Bay area up to nearly 7% in the New York City metro area, based on analysis of previously gathered blood samples.
Those numbers far outpace reported case counts but unfortunately still aren't broad enough to promote herd immunity, the point at which enough people are immune to a virus to protect those who haven't been either sick or vaccinated, according to an editorial accompanying the study.
"The study rebukes the idea that current population-wide levels of acquired immunity [herd immunity] will pose any substantial impediment to the continued propagation of SARS-CoV-2 in the U.S., at least for now," wrote Dr. Tyler Brown and Dr. Rochelle Walensky, infectious disease experts at Massachusetts General Hospital in Boston.
"The size of the epidemic projected through early May 2020 in this study falls far short of the estimated herd immunity threshold of approximately 60% to 70% -- 7 of the 10 study locations are currently experiencing substantial, as-yet uncontrolled increases in new COVID-19 cases," the editorialists wrote.
There are currently more than 3.8 million reported cases of COVID-19 in the United States, and nearly 141,000 deaths, according to the New York Times.
For the study, public health officials retested blood samples taken between March and May by two commercial clinical laboratories from sites across the nation, looking for antibodies that would reveal previous COVID-19 infection.
They then compared the evidence of infections they found to the actual case counts reported in those areas at the time the samples were drawn.
The number of infections outpaced reported cases by:
- Sixfold in Connecticut,
- Sevenfold in the Philadelphia metro area,
- Ninefold in the San Francisco Bay area,
- 10-fold in Utah and the Minneapolis-St. Paul-St. Cloud metro area,
- 11-fold in Western Washington and South Florida,
- 12-fold in the New York City metro area,
- 16-fold in Louisiana,
- 24-fold in Missouri.
"It has always been the case that we were missing a great number of coronavirus cases throughout the pandemic, and still are," said Dr. Amesh Adalja, a senior scholar with the Johns Hopkins Center for Health Security. "This new study cements the fact that our case counts are off by at least 10-fold and maybe even more."
The study underscores the need to drastically expand coronavirus testing in the United States, both Adalja and the Boston editorialists said.
"Understanding the true burden of disease is very important when trying to calculate hospitalization and mortality ratios and plan for the future," Adalja said, adding that the study "really underscores the need to become more aggressive in diagnosing and contact tracing individuals if we are ever to get a handle on the spread."
The United States will need to increase its viral testing capacity nearly 18 times more, becoming able to test approximately 4.3 million people each day, to effectively suppress further disease transmission, according to estimates cited by Brown and Walensky.
The U.S. Centers for Disease Control and Prevention have more about COVID-19.
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