Following major outbreaks at nursing homes in Walnut Creek and Concord, long-term care facilities now account for a staggering 70% of COVID-19 deaths in Contra Costa County, according to the county’s health department.

Twelve patients have died from COVID-19 at the ManorCare Health Services-Tice Valley nursing home in Walnut Creek, state health department information shows. In all, 92 patients and 38 health care workers were infected, and 25 patients are still sick.

At San Miguel Villa nursing facility in Concord, 20 patients and at least one health care worker have died, according to the state’s information; though the facility saw 65 patients and 17 workers become infected, no one there currently has COVID-19.

According to Contra Costa Health Services, 71 of the 102 COVID-19 deaths in the county involved long-term care facilities.

The 70% rate in Contra Costa is significantly higher than the rate of COVID-19 deaths that nursing homes and assisted living facilities account for in the statewide total — 46%.

San Mateo County’s data shows a rate almost as high as Contra Costa’s. In San Mateo County, 78 of the 114 people who have died from COVID-19 were associated with long-term care facilities — roughly 68%

In that county, an outbreak at Millbrae Skilled Care resulted in the death of 17 patients and at least one health care worker, according to the state’s information portal. The facility saw 103 patients and 32 staff members become infected.

In Santa Clara County, 81 of the 181 COVID-19 deaths have been traced to long-term care facilities, or about 45%. That’s the same percentage as in Alameda County, where nursing facilities accounted for 77 of 173 COVID-19 deaths.

The death toll across California skilled nursing facilities has reached 3,013 patients and 113 health care workers, according to the state. At least 17,162 patients and 12,202 health care workers in those facilities have tested positive for COVID-19 so far. Among residential care facilities for the elderly — commonly called assisted living facilities — an additional 5,215 residents and staff have contracted COVID-19, and at least 553 of them have died.

Months into the coronavirus pandemic — well after nursing facilities were instructed by health officials in March to ban visitors and stop all group activities — many nursing home and assisted living facility residents continue to get sick.

That’s because as COVID-19 spreads in the general population, health care workers are more likely to carry the coronavirus — often asymptomatically — into the nursing facilities where they work, experts say.

“The moment I saw increased community spread, I knew it would translate to more older adults dying, particularly in (nursing homes),” said Dr. Michael Wasserman, a geriatrician and president of the California Association for Long Term Care Medicine.

He pointed out that in addition to more COVID-19 cases, the number of nursing homes across California with large outbreaks has increased too.

“If nursing homes aren’t doing enough testing and frequently enough, they won’t pick up the asymptomatic people,” said Charlene Harrington, a professor and researcher at UCSF’s school of nursing. “So the key question is, how many of the nursing homes are actually doing the testing?”

A spokeswoman for ManorCare Health Services said everyone in the Tice Valley facility was tested and measures taken to offset the outbreak, including increased sanitization procedures and symptom and temperature checks, among other protocols suggested by health officials.

Contra Costa County issued a health order at the end of May requiring baseline testing of all residents and staff of a nursing home or other residential care facility. For those with positive cases, staff must be tested weekly until there are no new cases, but after that a facility “may resume its regular surveillance testing schedule.” It’s unclear how many facilities have their own regular testing schedules, if any.

Statewide, the California Department of Public Health has issued guidance for testing but ultimately has left testing up to facilities to coordinate with local health departments. There is also the issue of maintaining enough protective equipment such as masks, gloves and other gear for health care workers, which nursing facilities and assisted living communities struggled to acquire in the early days of the pandemic.

Harrington said there’s also still too little transparency and accountability about whether facilities have adequate supplies, staffing or testing.

“There is no penalty for not reporting, for a shortage of staff, for not doing testing,” she explained. While many nursing homes are being “extremely careful,” it’s entirely up to a facility’s ownership and management to protect staff and residents.

It hasn’t helped that facilities shut out family visitors and patient advocates in March to curb the spread of the coronavirus, she added.

So long as cases continue to rise in the communities, it is unlikely nursing facilities or assisted living facilities will start swinging the doors open again.

“As long as we have the spread out in the community,” nursing home patients will be affected, Harrington said.