We now have the first data to come out of mass testing of Mission District residents and workers last week, and out of 4,160 people who were tested both for COVID-19 infections and for antibodies, just over 2 percent tested positive for an active infection.

The data shows that the vast majority of those with infections — 90 percent — were people who had to work outside of their homes, and 95 percent in this case were Latinx, as the Chronicle reports. And over half — 53 percent — were asymptomatic or had not yet shown any symptoms. So that's alarming. Up to now the CDC has estimated that around 25 percent of cases may be very mild or asymptomatic.

The testing occurred over four days last week and was made available to everyone who lives or works between between South Van Ness and Harrison Streets, between 23rd Street and Cesar Chavez Boulevard. Results of antibody tests will be made available at a later date, but now we're hearing about the active COVID-19 cases that were found. With 2 percent testing positive, that means there were 87 COVID-positive cases found, and of those, around 46 showed no symptoms.

The Chronicle notes that 6.1 percent of workers in the neighborhood were positive for the virus, while only 1.4 percent of residents were positive. In all, about 55 percent of residents in this part of the Mission received a test.

The testing by UCSF in the Mission District followed similar mass testing in the North Bay town of Bolinas, where nearly all of the town's 2,000 residents received a test. No active cases of the virus and no antibodies were found among the insular community there.

Antibody testing that has occurred in Santa Clara County and New York has found large numbers of people who were previously infected with the coronavirus and perhaps did not know they were sick. In Santa Clara County, testing revealed 1.5 percent of those tested had antibodies, which researchers adjusted up to assume it represented 2.5 to 4 percent of the county population.

Previously: UCSF Study Will Give Free COVID-19 and Antibody Tests to Mission District Residents, Bolinas Residents