Antibody studies suggest coronavirus may be much more widespread than early estimates

Scientists out of Stanford say infections may be 85 times higher than confirmed cases.

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Health care workers in a drive-through coronavirus test
Health care workers in a drive-through coronavirus test in CA
(Bob Riha Jr/Getty)
Last Updated:
April 18, 2020 - 12:28pm

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Two studies this week from opposite sides of the United States suggest that the true coronavirus infection rate may be vastly higher than the number officially confirmed through medical testing, a sign that the country may be much further through the outbreak than it currently appears to be. 

Researchers out of Stanford University on Friday published the results of a 3,300-person testing project in Santa Clara County, California. That county was among the first in the nation where "community spread" of the disease was detected by public health officials. 

The study revealed that as many as 81,000 individuals in the county were likely infected with COVID-19 over the past few months, significantly higher than the 1,833 confirmed cases in the region as of Friday. The researchers estimated as many as 4.16 percent of all residents in the county have contracted the disease. 

"The population prevalence of SARS-CoV-2 antibodies in Santa Clara County implies that the infection is much more widespread than indicated by the number of confirmed cases," the scientists concluded. "Population prevalence estimates can now be used to calibrate epidemic and mortality projections."

The number of actual coronavirus cases in the country is a critical piece of the ongoing pandemic puzzle. The disease's fatality rate here, based on the number of confirmed cases versus the number of confirmed deaths, is hovering around 4 percent, significantly higher than that of the seasonal flu. Yet scientists have pointed out that the true number of cases is likely much higher than the confirmed number, which if true would send the fatality rate tumbling. 

Across the country, in Chelsea, Massachusetts, meanwhile, researchers this week say that 30 percent of 200 volunteers in a recent blood sample study tested positive for coronavirus antibodies. Chelsea, which sits just across from Boston, has recorded around 700 positive cases of the virus. 

The high antibody rates among these population is paradoxically good news from an epidemiological perspective: It means far more people have both contracted the disease and have largely recovered from it than health officials have currently confirmed. That suggests that these regions, and the United States as a whole, may be significantly further through the pandemic than official numbers indicate. 

Dr. John Iafrate, one of the principal investigators of the Chelsea study, told the Boston Globe that the high number of antibodies discovered there were a welcome sign.

"[I]t suggests that Chelsea has made its way through a good part of the epidemic. They’re probably further along than other towns," he said.