Hand of researcher holds test tube with blood for Coronavirus 2019-nCOV test.

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LOS ANGELES — Confirmed coronavirus cases only tell a portion of the story in any area, but a new study out of Los Angeles County has come to a startling conclusion. Based on the first round of antibody testing, 4.1% of the county’s entire adult population has already come into contact with the virus and developed an antibody.

After adjusting for statistical margin of error, that means anywhere from 221,000 to 442,000 local adults in Los Angeles have been infected by the coronavirus. That number is 28 to 55 times higher than the 7,994 confirmed COVID-19 cases in LA at the time the study was conducted earlier this month.

This research, performed by the University of Southern California, has a number of implications. Besides just documenting how widespread the coronavirus has become, it also suggests a lower fatality rate. As of today there have been just over 600 COVID-19 related deaths in Los Angeles county.

“Though the results indicate a lower risk of death among those with infection than was previously thought, the number of COVID-related deaths each day continues to mount, highlighting the need for continued vigorous prevention and control efforts,” explains Paul Simon, chief science officer at the L.A. County Department of Public Health and co-lead on the study, in a release.

“We haven’t known the true extent of COVID-19 infections in our community because we have only tested people with symptoms, and the availability of tests has been limited,” adds lead investigator Neeraj Sood, professor of public policy at the USC Price School for Public Policy and senior fellow at the USC Schaeffer Center for Health Policy and Economics. “The estimates also suggest that we might have to recalibrate disease prediction models and rethink public health strategies.”


Antibody tests can detect past infections, but PCR tests are the only way to identify an active case right now.

To come to these conclusions, drive-thru antibody testing sites were set up at six locations across LA county on April 10th and 11th. Tested locals were gathered from a database that is representative of the county’s population.

While these findings have not yet been peer-reviewed, the study’s authors plan to continue testing more residents in the coming weeks to get a better idea of the coronavirus’ spread throughout Los Angeles.

“These results indicate that many persons may have been unknowingly infected and at risk of transmitting the virus to others,” comments Barbara Ferrer, director of the L.A. County Department of Public Health. “These findings underscore the importance of expanded polymerase chain reaction (PCR) testing to diagnose those with infection so they can be isolated and quarantined while also maintaining the broad social distancing interventions.”

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About John Anderer

Born blue in the face, John has been writing professionally for over a decade and covering the latest scientific research for StudyFinds since 2019. His work has been featured by Business Insider, Eat This Not That!, MSN, Ladders, and Yahoo!

Studies and abstracts can be confusing and awkwardly worded. He prides himself on making such content easy to read, understand, and apply to one’s everyday life.

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