Study: Over 4% of LA County population may have been infected

California is among the states that have been hardest hit by the coronavirus pandemic. In Los Angeles County, more than 15,000 people have tested positive for COVID-19, but health officials announced this week that antibody tests show the rate of infection could be 40 times that number. 

Serology tests were used in a study conducted earlier in April by the University of Southern California and the LA County Public Health Department. The tests, which detect antibodies in an individual’s blood to determine if that person had the coronavirus, showed roughly 320,000 people, or about 4% of Los Angeles’ population, have been infected with COVID-19, CBS Los Angeles reports.

As of Tuesday night, there were 663 coronavirus deaths reported in Los Angeles. More than 45,000 people have died from the virus nationwide. 

Los Angeles Public Health Director Barbara Ferrer told reporters Monday that the serology tests provide “a better understanding” of how much of the city’s populations has been infected with the virus, “regardless of whether they were ever tested or they even had symptoms.” 

“So although I report that every day we have thousands of thousands of people who have tested positive, the serology testing lets us know that we have hundreds of thousands of people that have already developed antibodies to the virus,” said Ferrer. “Because at some point in time during the last couple of months, they have in fact been infected with COVID-19.”

According to CBS LA, the study was conducted between April 10 and April 14.

While many health officials say the blood-based tests are key to re-opening the economy, others say the high demand for the tests has pushed the FDA to favor speed over accuracy, and that many tests on the market are not regulated. As a result, the accuracy of some serology tests has been put under significant scrutiny nationwide.   

According to Reuters, a high number of false positives from antibody testing kits have been reported. In addition to skewing the data, this could lead some to believe they are immune to the disease when they are not. 

“Even a very small false positive rate could lead to hundreds of thousands of people being told that they’re safe when they might not be,” Dr. Ania Wajnberg of Mt. Sinai in New York told “CBS Evening News.”

Neeraj Sood, a professor of public policy at USC, and the lead researcher of the Los Angeles study, told Reuters that, by their estimates, “We might have to recalibrate disease prediction models and rethink public health strategies.”

“We haven’t known the true extent of COVID-19 infections in our community,” Sood said, “because we have only tested people with symptoms and the availability of tests has been limited.”

New York Governor Andrew Cuomo also addressed antibody testing in his state Tuesday, stating that such testing would be useful to determine the true number of people were infected with COVID-19 and what the actual mortality rate is.