L.A.’s COVID-19 Infection Rate May Be 55 Times Higher Than Previously Confirmed

Antibody testing suggests that many more people have been exposed to the virus

It has been known since the outset of the pandemic that the number of clinically confirmed cases of COVID-19 only represents a fraction of the total population that has been infected with the virus. Today, L.A. County Public Health provided new insight into just how small that fraction may be. According to a new study using antibody testing, experts are estimating that the total number of people infected could be 28 to 55 times higher than previous number of positive test results.

This new information comes via a study conducted by Public Health and USC relying on conducting antibody tests on a representative sample of the county population, regardless of whether the selected individuals have ever shown symptoms. What the scientists found indicates that an estimated 2.8 to 5.6 percent of adults in the county are already carrying the COVID-19 antibody.

Since antibodies develop from being exposed to the virus, that would suggest that 221,000 to 442,000 adults have had COVID-19. At the time results of this study were reached, earlier this month, only 7,994 cases of the virus had been confirmed via traditional testing. That number is now up to 13,816.

“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,” USC professor Neeraj Sood, a lead investigator on the study, stated in a press release about the findings. “The estimates also suggest that we might have to recalibrate disease prediction models and rethink public health strategies.”

If the findings, which have yet to be peer-reviewed by other scientists, are correct, it underscores the risk of individuals being out and transmitting the virus to others without ever knowing their own infection status–just as some communities are beginning to consider rolling back stay-at-home orders.

Antibody testing is seen as one key tool in grappling with the pandemic and determining when it may be safe to resume normal life, but there is evidence that the presence of antibodies in a patient does not make them immune to reinfection and some concerns have been raised about the accuracy and consistency of the tests themselves.

But there is some good news, too. The study suggests that the rate at which people who become infected with COVID-19 ultimately die may be lower than was previously thought. Nonetheless, experts warn it’s important to stay vigilant.

“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,” Dr. Paul Simon, chief science officer at L.A. County Department of Public Health and co-lead on the study, said.

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