The number of nursing homes publicly reporting cases of covid-19 has doubled in the past week, with more than 1 in 6 facilities nationwide now acknowledging infections among residents or staff, a Washington Post analysis of state and federal data found.

The rise is driven in part by newly released information about previous novel coronavirus infections from states including Michigan, Maryland, Kentucky and South Carolina. Some states have not yet publicly released the names of affected nursing homes.

In five states — Maryland, Massachusetts, Connecticut, Georgia and New Jersey — the virus has struck a majority of nursing homes, the data shows. In New Jersey, second only to New York in total number of confirmed coronavirus cases, health officials have reported infections at 80 percent of the state’s homes.

Maryland released a list earlier this week of more than 130 nursing homes with cases, about 60 percent of homes in the state. Overall, Maryland reported 185 long-term care facilities with cases.

Covid-19, the illness caused by the novel coronavirus, has been especially deadly for the elderly as it spreads across the world. State health officials have been slow to publicly identify nursing homes with positive cases, but in recent days, prodded by the Centers for Medicare and Medicaid Services (CMS), more states have released the names of facilities.

The tally paints a grim picture of the scale of the outbreak in homes tasked with caring for the elderly and infirm. More than 2,700 ­Medicare-certified nursing homes had publicly reported cases as of Tuesday, The Post found.

“People who work in nursing homes didn’t have the proper equipment and there wasn’t widespread testing,” said Laurie Facciarossa Brewer, the long-term care ombudsman in New Jersey. “Without those two critical components, you cannot avoid such a devastating outcome.”

The Post is updating a searchable database of Medicare-certified nursing homes that have at least one reported case of the coronavirus among patients or staff, using state lists and media accounts of local outbreaks. The count is incomplete. In New York, officials are releasing the names of only homes with at least five deaths, citing patient confidentiality. Virginia has released a total count of all long-term care facilities with covid-19 cases but has declined to name them.

Last week, CMS announced a mandate for nursing homes to report cases of covid-19 to families, patients and the federal government. CMS Administrator Seema Verma said the information would be made public, but it’s not clear when that might happen.

Thousands of other long-term care facilities, such as assisted-living centers and group homes, also are scrambling to slow the spread of the virus. The Post focused on nursing homes and skilled nursing facilities that are certified by Medicare and Medicaid, more than 15,000 nationwide.

The federal government has not released a count of fatalities at nursing homes, but in New York and New Jersey alone, more than 5,000 people at such facilities have died.

Earlier this week, Sen. Elizabeth Warren (D-Mass.) and two other lawmakers called on CMS to address “systemic failures” at nursing homes that are part of regional or national chains.

In a letter to Verma, the CMS administrator, lawmakers cited the Life Care Center of Nashoba Valley near Boston, saying more than 90 residents and staff members had tested positive and at least 17 had died. The facility is operated by Life Care Centers of America, which also operates the nursing home in Kirkland, Wash., that has been linked to more than 40 deaths.

“At both LCCA facilities, the operators did not provide adequate notification to public health authorities on any confirmed or suspected cases within their network,” Warren, Sen. Edward J. Markey (D-Mass.) and Rep. Lori Trahan (D-Mass.) wrote in their letter. “. . . In this unprecedented global pandemic, transparency and accountability is crucial to saving lives and safeguarding public health.”

Trahan told The Post that health officials in Massachusetts learned of the severity of the outbreak at Life Care’s Nashoba Valley facility only by cobbling together reports from local media and first responders.

“We don’t have time to lose during this pandemic,” she said. “We need federal oversight to intervene in a serious way.”

Tim Killian, public information liaison for Life Care Centers of America, said that the nursing home in Nashoba Valley had early, regular contact with public health officials in Massachusetts and that the lawmakers who wrote to CMS have “incomplete information.”

“It’s totally inaccurate,” he said of the letter. “Increased oversight is something we welcome in working with CMS. We invite any local or public health officials to contact us directly whenever they have questions about what is happening.”

Killian added that the nursing home is “presumptively clean,” meaning that everyone who was previously tested has not shown symptoms in more than three weeks.

As the scope of the crisis in nursing homes becomes clearer, some states are responding to calls for enhanced safety measures and better oversight. In Maryland on Wednesday, officials announced that the state would mandate coronavirus testing for the residents and staff of all nursing homes.

Massachusetts Gov. Charlie Baker (R) announced earlier this week that the state will spend $130 million to support infection control efforts and costs for personal protective equipment in nursing homes. The Massachusetts House of Representatives also has passed a bill requiring long-term care facilities to provide daily updates on the number of residents and staff members who have tested positive for or died of the virus. The proposal is now under consideration by the state Senate.

“We’re not going to be able to save every life, but we can certainly save more,” said state Rep. Ruth Balser (D), who co-chairs the Joint Committee on Elder Affairs.

In Connecticut, the National Guard and the Centers for Disease Control and Prevention are inspecting each of the state’s 215 nursing homes for lapses in infection control, according to local media reports. More than 60 percent of nursing homes in Connecticut have reported cases of the virus, The Post found.

The American Health Care Association and the National Center for Assisted Living, the trade group that represents more than 14,000 long-term care facilities, is pressing for more government support to address the outbreaks, including additional staff, supplies, emergency funding and widespread testing to identify residents and staff members who are asymptomatic carriers of the virus.

In a call with governors on Friday, Vice President Pence said the Federal Emergency Management Agency was preparing to send personal protective equipment, including gloves, masks and protective eye gear, to all 15,000-plus nursing homes, according to ABC News.

For weeks, industry leaders say, nursing homes have been largely left to fend for themselves.

“Just like hospitals, we have called for help. In our case, nobody has listened,” Beth Martino, AHCA senior vice president of public affairs, said in a statement.

In New Jersey, some overwhelmed nurses can barely find time to provide updates to worried families, said Brewer, the state’s long-term care ombudsman.

“The issue of notifying people is overwhelming,” she said. “Calls have gone from, ‘I don’t know if my mother has a fever,’ to ‘I don’t know if they’re dead or alive.’ ”

In the District, where about 15 nursing homes have reported cases, David Sherman said he is still trying to find out more about the status of his 89-year-old mother, who tested positive last week.

Marie Dowden lives at Stoddard Baptist Nursing Home in Northwest Washington. On Tuesday, the administrator for the home said 11 residents and 16 staff members had tested positive. Sherman said he doesn’t know when his mother was tested or how the facility plans to provide ongoing care.

“You had me at a horrible disadvantage,” he said of the nursing home. “I can only rely on the information that you’re giving me, and you’re only giving me bits and pieces.”

Nursing home administrator Remy Johnson said staff members are monitoring residents for signs of illness, following CDC guidelines, and communicating with families through letters and robocalls. She recalled speaking to Sherman in recent days and said that nurses, social workers and other supervisors are also available.

“There are different people that they can connect with,” she said.

For weeks, nursing homes across the country have been on lockdown, limiting the number of visitors. Sherman said he’s desperate for more information about his mother, a dementia patient.

“It’s driving me crazy that I can’t get any answers,” he said.

Jacobs, Mulcahy and King are graduate students in journalism at Northwestern University’s Medill Investigative Lab. Alexa Mikhail and Dan Rosenzweig-Ziff from the Medill Investigative Lab contributed to this report.