from RT:

A study out of Stanford University tested California residents and found that the Covid-19 infection rate is likely far higher than has been reported, but the virus could also be far less lethal than commonly believed.

Researchers used 3,300 residents in Santa Clara County to conduct their tests, which found that the coronavirus could have infected far more people than has been reported. The study distinguishes itself from past Covid-19 research by using seroprevalence data, meaning the level of a pathogen measured in the blood streams of a specific population.