On Apr. 20, 2020, University of Southern California (USC) and the Los Angeles County Department of Public Health released preliminary results from a collaborative scientific study that suggests infections from the new coronavirus are far more widespread – and the fatality rate much lower – in L.A. County than previously thought. Based on results of the first round of testing, the research team estimates that approximately 4.1% of the county’s adult population has antibody to the virus.

Adjusting this estimate for statistical margin of error implies about 2.8% to 5.6% of the county’s adult population has antibody to the virus— which translates to approximately 221,000 to 442,000 adults in the county who have had the infection. That estimate is 28 to 55 times higher than the 7,994 confirmed cases of COVID-19 reported to the county by the time of the study in early April. The number of COVID-related deaths in the county has now surpassed 600.

With help from medical students from the Keck School of Medicine of USC, USC researchers and Public Health officials conducted drive-through antibody testing April 10th and 11th at six sites. Participants were recruited via a proprietary database that is representative of the county population. The database is maintained by LRW Group, a market research firm.

The researchers used a rapid antibody test for the study. The FDA allows such tests for public health surveillance to gain greater clarity on actual infection rates. The test’s accuracy was further assessed at a lab at Stanford University using blood samples that were positive and negative for COVID-19.

The study was supported with funding from USC Schwarzenegger Institute, USC Lusk Center, USC President’s Office, Jedel Foundation, LRW Group, Soap Box Sample, and several individual donors.