Maryland announced Wednesday that it will test all nursing home residents and staffers for the novel coronavirus, which has spread through 194 facilities, infecting 4,822 staff members and residents and killing 516. Officials said the state may be the first in the country to mandate universal testing.

Data released Wednesday evening showed that half of Maryland’s confirmed covid-19-related deaths and more than a fifth of its cases were linked to skilled-nursing facilities. That is a higher percentage than in California, where about 30 percent of deaths have been linked to nursing facilities, and in New York, where the figure is about 20 percent.

A report from the Kaiser Family Foundation found on the basis of preliminary analyses that 27 percent of the nation’s coronavirus deaths have been linked to facilities that provide long-term care.

The Maryland data, made public after relatives and advocates for nursing home residents called repeatedly for greater transparency, provides startling evidence of the scale and severity of outbreaks in the state.

Relatives of care-center residents who have died of the virus said the data raises new questions about whether state and local authorities provided adequate support to nursing homes as the pandemic arrived in the region, and about what, if anything, can be done to curtail the further spread of the virus among residents and employees.

“It certainly doesn’t seem like [officials] did enough,” said Montgomery County resident Barbara Joltin. Her husband, Steve Joltin, died April 11 of covid-19 at the Rockville Nursing Home, where 50 others have been infected and nine have died.

“Looking at this data, there’s a ‘what if,’ you know?” Joltin said, holding back tears. “What if he hadn’t been in that nursing home? Would he still be alive?”

A receptionist at Rockville Nursing Home said no one was available to provide comment Wednesday and directed a reporter to the nursing home’s website.

An executive order from Gov. Larry Hogan (R) makes Maryland one of the first states to mandate universal testing of all nursing home residents and employees. Employees who test positive will immediately be asked to self-isolate. To supplement staffing shortages, Maryland is deploying to various facilities “bridge teams” of 260 state-contracted nurses and health aides, an initiative announced Wednesday.

“We are no longer playing defense. We are going on offense, attacking it from every angle, with everything we’ve got,” Hogan said.

He added that the Maryland National Guard state surgeon, Eric B. Allely, will lead an interagency team of officials to ensure that nursing homes comply with new state rules requiring testing and regular communication of information to patients’ families.

“[Universal testing is] too late,” said Herman Taylor, whose sister lives at Regency Care of Silver Spring, a 92-bed facility where 30 staffers and 50 patients have been infected, 10 of whom have died. “It’s certainly too late at Regency — everybody has it. . . . I still have no idea what the game is to get everybody healed.”

Nursing homes in Montgomery County, the state’s most populous jurisdiction, reported 1,099 confirmed infections and 149 fatalities across 48 facilities — accounting for two-thirds of the county’s covid-19 deaths. Baltimore County reported 832 cases and 71 deaths.

The largest nursing home death toll is at Sagepoint Nursing & Rehabilitation in La Plata, where 35 have died.

Local officials say Montgomery was particularly hard-hit in part because there are more long-term care facilities in the county, where 1 in 7 residents are 65 or older. But some also said authorities could have done more to monitor infection-control measures at nursing homes before the pandemic and could have provided more support when facilities first reported cases.

Others say it has been difficult to respond to outbreaks because of a lack of information from state officials about what Hogan’s nursing home “strike teams” have been doing since their creation about three weeks ago.

“It’s clear that the systems we had in place were not built for what we’ve seen,” said Montgomery County Council member Gabe Albornoz (D-At Large), who chairs the council’s health and human services committee. “We need to make sure that there is a complete and total evaluation of not just how we responded to this virus but the systemic issues that existed in this entire system even before covid-19.”

Nursing home residents, who are often elderly and have underlying ailments, are exceptionally vulnerable to covid-19. Many of the facilities where they live are understaffed and unprepared to manage severe viral outbreaks. A recent analysis by The Washington Post found that at least 40 percent of nursing homes with known outbreaks in the country have been cited more than once by inspectors in recent years for violating federal standards meant to control the spread of infections.

In Maryland, the virus raced in a matter of days through Pleasant View Nursing Home in Carroll County, which struggled with shortages of staff and personal protective equipment. Twenty-nine patients ultimately died. Outside Richmond, an even larger outbreak has claimed the lives of at least 40, and the director said society is partly to blame because of its willingness to “warehouse” the elderly in underfunded public facilities.

At least 30 percent of all infections and deaths at Maryland nursing homes can be traced to 13 facilities. An analysis of the state data by The Post shows that none of those 13 facilities provided ventilator care, which is offered at only 11 percent of nursing homes statewide.

Among the facilities with the deadliest outbreaks are Manor Care of Silver Spring, a 148-bed facility with 75 infections and 16 deaths; and Regency Care of Silver Spring.

Regency has an overall rating of two out of five stars from Medicare and a one-star rating based on recent health inspections. Manor Care has an above-average rating of five out of five stars from Medicare, as well as a below-average number for health citations.

Multiple calls to both facilities have gone unanswered in recent weeks. On Wednesday, receptionists at each nursing home said organization leaders were in meetings and not immediately available to answer questions.

“Quite frankly, there needs to be a formal investigation of the facilities where we’ve had significant outbreaks,” Albornoz said. “We need to assess what transpired. Were laws broken or rules not followed?”

Nursing homes say they have struggled to respond to the virus because of a lack of testing and personal protective equipment.

Until early April, federal guidelines suggested that the virus was unlikely to spread among asymptomatic people, said Montgomery County Health Officer Travis Gayles. As such, the county did not require all nursing home employees to be masked at all times or to wear full protective equipment even if there were known outbreaks at the facility.

Because of the lack of testing materials, officials were unable to proactively test nursing home workers who were asymptomatic, he said, which may have allowed health-care workers to carry the virus among facilities undetected.

The county introduced “tougher precautions” this month, mandating that all nursing home employees wear face coverings at all times and distributing protective equipment to all long-term-care facilities. It also added staffers to its “action teams” of county nurses, which provide assistance to nursing homes with known coronavirus cases.

“When you look at the numbers, you can get the inference that we haven’t been actively engaged [with these facilities],” Gayles said, “That’s not true.”

Joseph DeMattos, president of the Health Facilities Association of Maryland, said nursing homes should receive the same amount of government support as hospitals, including in terms of “financial assistance, testing and critical supplies of PPE.”

He also noted, however, that many elderly nursing home residents have underlying ailments that make them particularly susceptible to the virus. Some have also signed orders not to be resuscitated or intubated, which may prevent doctors from providing certain kinds of medical assistance.

“Any death is tragic and sad,” he said. “But given the ferocity of the virus . . . these numbers weren’t surprising to me.”

Hogan announced in early April that he was launching strike teams of state employees to assist nursing homes in need of support.

As of Wednesday, the state has sent these teams to 84 facilities, including nine in Montgomery, Gayles said.

Montgomery County Council Vice President Tom Hucker (D-District 5) said he has found it difficult to get information on what the state strike teams have found during site visits and what they are doing to assist facilities.

“I’m struggling to get information, and if I’m struggling, I can be sure that there are a few hundred thousand constituents who are struggling, too,” he said.

Rachel Chason contributed to this report.