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More than half of those who tested positive for the coronavirus at institutional settings in Los Angeles County did not have any symptoms of the respiratory illness, the county’s public health director said Thursday.

Dr. Barbara Ferrer said that in many facilities where both symptomatic and asymptomatic people were tested, the majority of people who were found to be positive were asymptomatic.

This includes people at the Union Rescue Mission in downtown L.A., which reported Skid Row’s first confirmed COVID-19 case nearly a month ago and now has at least 56 confirmed cases.

“Our numbers have gone up dramatically, but many of the people who tested positive — more than half so far — didn’t present with any symptoms at all,” Ferrer said, adding that this underscores the need for increased testing at facilities.

There were 286 institutional settings with at least one case of COVID-19 in L.A. County as of Thursday. Together, the facilities have reported a total of 3,343 cases of the respiratory illness and 310 deaths — that’s about 39% of all COVID-19 fatalities in the county.

Ferrer said most of those people who died lived in skilled nursing facilities.

Besides nursing homes, institutional settings include homeless shelters, correctional facilities and treatment centers.

While residents can only get tested for the coronavirus at the county’s drive-up and walk-in sites if they have symptoms of the illness, the health department started testing staff and residents at nursing homes who don’t have symptoms, as many of the facilities across the county reported outbreaks.

Nearly half of the county’s more than 300 skilled nursing facilities have reported infections among both staff and residents, according to a list released by the California Department of Public Health.

Twenty-six of the skilled nursing facilities reported 20 or more COVID-19 cases among their residents, Ferrer said.

Officials said they hope that stepping up testing, among other measures, would help with quickly isolating the sick to stop the virus from spreading further.

“In the past, we have done a lot of our infection control protocols around the assumption that we needed to worry about people who are symptomatic and test people who are symptomatic,” Ferrer said at a Wednesday news conference. “But it turns out that we were wrong, and with new information it’s become clear that asymptomatic people are capable of spreading the virus.”

Symptoms of COVID-19 include fever, cough and shortness of breath, and may appear between two to 14 days after exposure, according to the Centers for Disease Control and Prevention.

Across all L.A. County, 17,508 people have tested positive for the coronavirus and 797 have died from complications from the illness it causes.

Over 98,000 people have been tested for COVID-19 in the county as of Thursday, and of those whose results were processed, about 14% were found to be positive, according to Ferrer.