The number of confirmed COVID-19 cases in Los Angeles County climbed past 31,600 Sunday with nursing homes still among the hardest hit in the epicenter of the coronavirus outbreak in California.

Nearly half of the 1,530 people known to have died because of COVID-19 in L.A. County had been living in settings where people are clustered close together. And the majority of them lived in nursing facilities, according to the county’s public health director Barbara Ferrer.

The Los Angeles County Department of Public Health on Sunday reported 484 new coronavirus cases and another 18 deaths attributed to the respiratory illness it causes.

There are at least 200 skilled nursing facilities in L.A. County that have had staff and residents test positive for the virus, according to the county’s health department, which keeps a running list of facilities with known cases.

The biggest virus cluster among the county’s nursing homes is at Brier Oak On Sunset, an East Hollywood facility where 72 employees and 79 residents have tested positive for the virus.

With those 65 and older and people with underlying health conditions being most vulnerable to serious illness as the coronavirus continues to spread countywide, officials in recent weeks have focused their efforts on expanding testing at all institutional settings in L.A. County, particularly at nursing homes.

They began testing all staff and residents, regardless of whether they showed any symptoms of the respiratory illness.

Ferrer has said that the majority of people who tested positive in such settings did not show symptoms of COVID-19.

But even as the county works to address the issue by increasing testing, Ferrer on Friday said there have been some barriers.

Many of the facilities have been grappling with staffing shortages that have made it difficult to prioritize testing asymptomatic people, she said.

Also, the facilities have been experiencing delays in getting testing kits when they try to order them on their own, according to the health director.

As of Friday morning, 95 of the more than 300 skilled nursing facilities in the county had been able to test all of their residents and staff.

Ferrer said that some of skilled nursing facilities have “designated themselves as COVID-19 facilities.” This means they’re open to receiving new COVID-19 patients from hospitals and other nursing facilities that need to transfer out some of their patients to ensure they can be isolated to prevent further infections.

To help address the staffing shortages at nursing homes statewide, staff from the U.S. Navy hospital, the USNS Mercy, started helping skilled nursing facilities in the L.A. area on Friday, Gov. Gavin Newsom announced.

Before that, 40 of the personnel were assigned off the ship to help a nursing facility in Orange County, according to USNS Mercy spokesman Lt. Andrew Bertucci.

The ship had arrived at the Port of L.A. on March 27 to provide relief to hospitals as officials feared a flood of COVID-19 patients that could overwhelm medical centers.

But as social distancing efforts took shape, later projections showed that local hospitals will be able to meet the demand for beds and ventilators in the coming weeks. As of Sunday, 5,410 people who tested positive for the coronavirus have needed hospitalization across the county.

The navy ship only ended up treating 77 patients and discharged its final patient Thursday, six weeks after docking, according to a news release.

“We’re still in Los Angeles supporting FEMA and state authorities and local agencies supporting skilled nursing facilities,” Bertucci said. “We’re still here to support the state of California and address whatever their needs are.”

It’s unclear how long the ship and its personnel will stay in Los Angeles.

So far, 92% of L.A. County’s residents who died from COVID-19 have had underlying health conditions.

Ferrer urged those with conditions that compromise their immune systems to stay home, even as the county moves towards reopening more locations.

“Each day, we report these numbers knowing that there are people who are grieving their loved ones who have passed away from COVID-19. To all of you, we are so deeply sorry for your loss,” Ferrer said in a written statement. “As we begin our recovery journey, we are grateful for all you have done to get us to this point. More than ever, we all need to continue to do our part to slow the spread of COVID-19, to protect the most vulnerable members of our community, and to, most importantly, save lives.”