Preliminary results from an antibody test conducted by the University of Southern California (USC) and the Los Angeles County Department of Public Health suggest coronavirus infections are more widespread than previously anticipated, but with a much lower fatality rate.
Researchers and public health officials conducted drive-thru antibody testing from April 10-11 at six locations. The results from the first round of testing, released Monday, showed approximately 4.1 percent of the county’s adult population has an antibody to the virus. Antibodies are a protein in the blood produced in response to a specific pathogen like the coronavirus.
When taking the statistical margin of error into account, about 2.8 percent to 5.6 percent of the county’s adult population is projected to have an antibody to the coronavirus. These percentages translate to about 221,000 to 442,000 adults in L.A. County who have been infected.
That estimate is about 28 to 55 times higher than the 7,994 confirmed cases of COVID-19 reported to the county at the time of the study. As of Monday, L.A. County had 13,816 confirmed cases of the coronavirus.
“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,” lead researcher Neeraj Sood said in a statement. Sood is also 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,” Sood added.
Antibody tests can detect past infections and exposure to the virus, but do not indicate whether a person is currently ill. An expanded polymerase chain reaction test is required to diagnose current infections.
Still, understanding how many people have been exposed to the coronavirus can help scientists and public health officials understand its movement, especially among asymptomatic carriers.
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“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,” Barbara Ferrer, director of the L.A. County Department of Public Health, said in a statement.
The study has not yet been peer reviewed. Researchers plan to test new participants every few weeks in the coming months to gauge the pandemic’s trajectory.
California Gov. Gavin Newsom (D) gave an update Monday on the state’s fight against the virus, saying that the curve is bending and beginning to flatten, but still rising.
“Deaths continue to rise, hospitalization numbers modestly continuing to rise and ICU numbers beginning to flatten,” Newsom told reporters. “But we’re not seeing that downward trend we need to see in order to provide more clarity on that roadmap to recovery which we rolled out last week.”
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