As thousands take to the streets of Los Angeles to protest police violence in light of George Floyd’s killing, the coronavirus pandemic continues to rage, with 1,445 new cases reported in the county Friday.

Health officials continue to worry that the close gatherings are likely to contribute to the spread of the coronavirus, and the impact won’t show for another three to four weeks — especially since access to testing has been limited in recent days.

Barbara Ferrer, director of public health for L.A. County, urged those out demonstrating to wear a snug-fitting cloth face covering and to make sure both their mouth and nose are fully covered.

“I want to thank everybody who is wearing a face covering. That offers a lot of protection,” she said addressing protesters Friday. “But obviously the best protection is both a cloth face covering, and the social distancing.”

Ferrer said those who find themselves in a crowded situation, especially around people who are not wearing cloth face coverings, have an increased risk of exposure. She urged people out at rallies to consider self-quarantining.

“That means that you would be staying home or in your residence away from other people as much as possible for the full 14 days to see whether you develop any symptoms,” she said, emphasizing that the virus has “a long incubation period” and may take the full 14 days for symptoms to become apparent.

“If you test negative for COVID-19 right after being exposed, it doesn’t mean you’re in the clear,” Ferrer said. “You could still become infected toward the end of the two-week window.”

Half of the 36 COVID-19 testing sites operated by the city and county were closed Monday, and were set to reopen Friday. The sites closed because volunteers weren’t signing up to run them amid the protests that intensified over the weekend, according to L.A. Mayor Eric Garcetti.

Still, more than 30,000 people were tested countywide this week, Garcetti said Thursday. But the sites have the capacity to test more than 25,000 people each day.

Densely-populated L.A. County remains the epicenter of the pandemic in California with 61,045 reported coronavirus cases and 2,565 deaths as of Friday.

As coronavirus continues to kill more black Americans than other racial groups, Ferrer said that racism has had a “devastating” impact on health for black residents.

“I think it’s important to comment on the connection between these two concerns, the death of a Black man at the hands of police, and the experience of COVID-19 in L.A. County,” she said. “The root cause of health inequities is racism and discrimination and how it limits access to the very opportunities and resources each of us need for optimal health and well-being.”