https://techcrunch.com/2020/04/20/l-a-covid-19-antibody-study-adds-further-support-for-a-higher-than-suspected-infection-rate/

A new study conducted by the University of Southern California along with the LA County Department of Public Health indicates that the presence of antibodies for COVID-19 in between 2.5 and 5.6% of the population of LA County, suggesting that between 221,000 and 442,000 individuals had the infection – up to 55 times more people than have been confirmed via testing. This is the second antibody study in a short span of time in California that suspects infections are far more widespread than previously thought, and a good justification for continued social distancing measures.

The LA County study does contain some good news, if the antibody testing proves to be accurate (we aren’t entirely sure what they show for sure at this point, especially in terms of immunity), in that the mortality rate of the infection is actually much lower than the official diagnosed case data would suggest. The infection rate found via antibody testing through the USC study is also remarkably close to the rate found in a Stanford study published last week about the number of infections in Santa Clara County, which found that between 48,000 and 81,000 people in that part of California could’ve had and recovered from the infection.