A new study from National Institutes of Health researchers suggests COVID-19 was more prevalent in the U.S. during the first six months of the pandemic than originally thought. Their estimate of actual COVID-19 cases is nearly five times higher than what was being reported from testing.
Their research estimates nearly 17 million people had COVID-19 and went undiagnosed in the first half of 2020. Data available at the time was only reporting about 3 million confirmed COVID-19 infections in the U.S.
The team analyzed blood samples from more than 8,000 volunteers taken between May and July 2020. The volunteers were never diagnosed with COVID-19, and their demographics reflect that of the general population.
Around 5% of the blood samples had coronavirus antibodies.
“A hallmark of the coronavirus pandemic is that there are people infected with the virus that causes COVID-19 who have few or no symptoms,” said Matthew J. Memoli, M.D., M.S., director, Clinical Studies Unit, Laboratory of Infectious Diseases, NIAID.
“While counting the numbers of symptomatic people in the United States is essential to contend with the impact of the pandemic and public health response, gaining a full appreciation of the COVID-19 prevalence requires counting the people who are undiagnosed.”
The team found that the younger participants, those between the ages of 18 and 44, had the highest proportion of antibodies compared to other age ranges.
There were also more females than males who had antibodies without a history of COVID-19 diagnosis.
When it came to ethnicities, Black Americans were more likely to have an undiagnosed infection, at 14.2% of those participants showing antibodies; Hispanic Americans were at 6.1%, white Americans at 2.5% and Asian Americans at 2%.
“The estimate of COVID-19 cases in the United States in mid-July 2020, 3 million in a population of 330 million, should be revised upwards by almost 20 million when the percent of asymptomatic positive results is included,” said senior co-author Kaitlyn Sadtler, Ph.D., chief of the NIBIB Section on Immunoengineering.
“This wide gap between the known cases at the time and these asymptomatic infections has implications not only for retrospectively understanding this pandemic, but future pandemic preparedness.”
The report is the first from a 12-month study with the NIH researchers.