As many as one-quarter of Americans may have contracted the novel coronavirus since the start of the pandemic, a new study suggests.
Current case counts show that 3.8 million people in the US have fallen ill with COVID-19, the disease caused by the virus, according to Johns Hopkins University.
But a team, led by the Centers for Disease Control and Prevention (CDC), says the true figure is actually between six and 24 times greater than the total of reported cases.
That’s anywhere between 22.8 million people and 91.2 million people.
However, despite the number of infections being greater than the number of confirmed cases, most specimens that were tested didn’t have antibodies, which researchers estimate is a mix of people who had a mild illness or no illness at all.
In a new study conducted across 10 states, the proportion of people with coronavirus antibodies ranged from 1.0% in the San Francisco Bay area to 6.9% in New York City (above)
The team says it believes this means the case count is actually between six and 24 times greater than the total reported number. Pictured: Stephanie Mundo draws blood during a COVID-19 antibody test at the Abyssinian Baptist Church in New York City, May 14
For the study, published in JAMA Internal Medicine, the team performed antibody testing on samples collected between March 23 and May 12.
Samples were taken in 10 places: San Francisco Bay area, California; Connecticut; southern Florida; Louisiana; Minneapolis-St Paul-St Cloud metro area, Minnesota; Missouri; New York City metro area, New York; Philadelphia metro area, Pennsylvania; Utah; and western Washington.
More than 16,000 people were tested for antibodies to the spike protein, which the virus uses to enter and infect human cells.
The proportion of people with antibodies ranged from 1.0 percent in the San Francisco Bay area to 6.9 percent in New York City.
In seven areas – Connecticut, Florida, Louisiana, Missouri, New York City metro area, Utah, and Washington – the number of infections was estimated to be 10 times greater than the number of cases.
The estimate was lowest in Connecticut, where infections were approximated to be six times greater than the 29,000 reported cases as of May 3.
The figure was highest for Missouri, where estimated cases were about 24 times higher than the nearly 6,800 cases reported as of April 25.
However, most of the 16,000 specimens did not show antibodies to SARS-CoV-2, meaning the majority of Americans are not immune.
The authors note that the study has some limitations, namely that samples were collected at different time periods, prior to some states’ peaks and in the middle of others’ peaks.
Regardless, they add that this is the first population-based study in the US that explains the regional differences in undetected coronavirus infections.
‘During March to early May 2020, most persons in 10 diverse geographic sites in the US had not been infected with SARS-CoV-2 virus,’ the authors wrote.
‘The estimated number of infections, however, was much greater than the number of reported cases in all sites.
‘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.’
In a linked editorial, Drs Tyler Brown and Rochelle Wolensky of the Division of Infectious Diseases at Massachusetts General Hospital in Boston, said the findings of the study dismiss the idea that the US has reached the level of herd immunity needed to control the spread of the virus.
Additionally, they note seven of the 10 locations studies are still experiencing uncontrolled increases in new COVID-19 cases.
‘These data should also quickly dispel myths that dangerous practices like “COVID parties” are either a sound or safe way to promote herd immunity,’ they wrote.
It comes as the Centers for Disease Control and Prevention (CDC) released a report on Tuesday, which determined that 2.79 percent of Indiana residents age 12 or older had a current or previous coronavirus infection in April 2020.
It was the first time a state had conducted a random sample study to determine the prevalence of the virus at a given point in time.
The CDC also revealed that it determined that 2.5 percent of two counties in metropolitan Atlanta have antibodies to SARS-CoV-2.