With more than 650 people infected with the coronavirus at local long-term care facilities, Riverside County on Monday released a list of assisted-living homes with large COVID-19 clusters.

Most of the confirmed cases at such institutions — 414 of them — are among residents at skilled-nursing facilities, with cases reported at 40 of the county’s 53 nursing homes, according to a news release from the county public health department.

Another 49 cases have been identified among residents at 14 assisted-living homes, and the remaining 211 known infections are among staff at the senior care facilities, officials said.

The county says it’s tested about 1,200 more residents at hundreds of other long-term care facilities. It did not report how many of those individuals tested positive.

The 674 cases reported at assisted-living and nursing homes represents about 19% of the 3,643 confirmed COVID-19 cases in Riverside County.

“We have known since the beginning of this response that congregate care facilities would provide one of the biggest challenges,” Kim Saruwatari, the county’s public health director, said in a statement.

Nursing homes across the nation have become hot spots for the outbreak, with their senior citizen residents — many of whom have compromised health — living in close quarters. As a result, nursing home residents account for a large portion of COVID-19 deaths nationwide.

Riverside County has not said how many of its 141 coronavirus deaths were among nursing home residents.

But in neighboring Los Angeles County, officials say 45% of all COVID-19 fatalities are linked to an institution, most of them skilled-nursing facilities. And, when that county began testing all residents and staff at the homes, officials reported more than half of those who tested positive didn’t have any coronavirus symptoms.

The state Department of Public Health names reports more than 3,400 positive cases and 545 deaths among residents at skilled-nursing homes.

Riverside County says it’s prioritizing senior care institutions in its pandemic response. Earlier this month, officials put out a call for volunteers to help staff nursing and assisted-living facilities.

County officials have also created four teams to provide outreach support to nursing homes, including helping out with staffing when necessary.

The groups are made up of workers from American Medical Response and health care providers, including behavioral health experts. They’ve visited more than 140 facilities to demonstrate safety techniques, provide gear and dispel misinformation surrounding the outbreak, according to Saruwatari.

Skilled-nursing facilities in Riverside County with large coronavirus clusters

The county has released a list of 12 nursing homes with the largest virus outbreaks.

The data is provided by the state Department of Public Health, which doesn’t include figures for assisted-living facilities or locations with fewer than 11 confirmed cases, according to Brooke Federico, a public information officer for Riverside County.