The state added three men to its count of coronavirus fatalities on Sunday, bringing the total to five as the known cases of the dangerous illness continue to rise in Massachusetts. The state Department of Public Health said it had recorded 646 cases in Massachusetts, up from 525 a day earlier.
The newly reported fatalities included a man in his 70s from Hampden County, a man in his 70s from Berkshire County, and a man in his 90s from Suffolk County, according to the Department of Public Health. All three men had been hospitalized with the illness, known as COVID-19.
The health agency said the Berkshire County patient had “an underlying health condition,” and that “all three men were in an age group that is more likely to experience severe disease from COVID-19 regardless of prior health status.”
The two previous deaths were an 87-year-old veteran from Winthrop and a woman in her 50s from Ayer, whom state officials said also had a health condition that put her at greater risk.
The population of people known to have COVID-19 has skewed older, according to state data. The majority of patients have been over 40, with 20.7 percent in their 40s; 18.4 percent in their 50s; 13.5 percent in their 60s; and 12.8 percent older than 70. People 19 or younger made up 2.8 percent.
Still, many patients were younger adults. About 31.7 percent were in their 20s and 30s.
State and local governments on Sunday were continuing to grapple with the spread of the dangerous respiratory illness that has sickened tens of thousands of Americans and brought life to a halt for tens of millions more.
Nantucket on Sunday became the first Massachusetts community to order its residents to remain at home after the report of a single known case of the virus. Given the town’s island location and its limited health care resources, local officials said they were taking forceful steps that could slow the spread of COVID-19.
“People could die from inadequate access to medical care if we don’t take these extreme measures,” Nantucket town leaders said in a statement.
The order will be in effect from 5 p.m. Monday "until further notice,” though it makes allowances including for people to get medical care or visit “grocery stores, pharmacies, and restaurants (including take-out and coffee shops — for delivery or curbside pick-up only).” The town also is considering restrictions on travel to and from the island starting Wednesday.
While Massachusetts has not issued a broad order for most residents to stay at home, states including California and New York have done so. And public officials in Massachusetts have barred most gatherings and encouraged people to remain at home whenever possible.
As the numbers rose over the weekend, the visible effect of the illness in Massachusetts continued to expand.
Boston police announced that an officer has tested positive for the coronavirus, and he will remain at home until he is medically cleared. Sergeant Detective John Boyle, a police spokesman, said it was not clear whether the officer had contracted the illness on the job or elsewhere. Police did not say where the officer was assigned, but Boyle said the officer’s workplace had been cleaned and disinfected following the positive test.
In Billerica, town officials reported that a local first responder had become the town’s fifth confirmed case of COVID-19. The person, who was not identified, had “responded to an earlier confirmed case,” according to the town government.
In health care facilities, staff were taking added precautions as they treat patients ahead of an expected surge of cases that could strain the system.
Massachusetts General Hospital, which treated the first Massachusetts patient to die from COVID-19, and all other hospitals in the Partners Healthcare network said they will require staff to wear face masks continuously while onsite.
Local hospitals reported only a few new cases of the virus on Sunday. Massachusetts General Hospital gained two new patients who had tested positive, for a total of 20. Across the Beth Israel Lahey Health system, the total went from 21 positive patients to 26. There were no new positive tests at Tufts Medical Center, which is treating two COVID-19 patients, and Boston Medical Center went from one patient to none.
Governor Charlie Baker said Sunday that the state is continuing discussions with the federal government over where and how to expand the capacity of the state’s medical system ― either by repurposing unused facilities or constructing field hospitals. He said his administration will propose potential sites within days and they could be up and running within two to three weeks if necessary.
The governor said he believes increased testing will be a key factor in limiting its spread even as harder-hit parts of the country are pulling back on testing for the general public amid fears that it may no longer be possible to contain the virus in some places.
“The goal here is to dramatically expand testing ... both in terms of who gets tested and how many people get tested, and then use that data to do tracing and isolation,” Baker told reporters. “That has been the strategy that has been most effective in other countries, and it’s got to be the core of the way we deal with this.”
The Massachusetts Department of Public Health said on Sunday at least 6,000 people had been tested for COVID-19 since the start of the crisis, an increase a day earlier, when the number stood at more than 5,200. Baker has set a goal of processing 3,500 tests daily.
Baker said the number of positive cases "is going to climb.”
“And the reason that they are going to climb is because we are testing more," Baker said. "That’s not necessarily a bad thing.”
The availability of testing has increased in recent days, but tests were in short supply when the virus began spreading in the United States. That constrained the information available to public health authorities and raised concerns that people might be spreading the virus without knowing they had it.
But officials in some areas have concluded that it may be too late for testing to play a major role in containment.
The Washington Post reported Saturday that areas including New York and California had begun limiting coronavirus testing to health care workers and the severely ill. Some are concerned that the medical interactions associated with the tests would use up needed medical supplies and potentially spread the virus further.
Baker said Sunday that he believes that more data about who has the coronavirus will improve the situation by making it easier to identify people who had been exposed to the patients, and then making sure those exposed people did not give it to more people.
Aggressive testing approaches are believed to have helped blunt the effect of the virus in other places, including South Korea, whose strategy has been credited with bringing down the number of cases.
Baker said during his news conference that the state is doing everything it can to “chase down” personal protective equipment for people who still must interact with other people as part of their jobs.
He said he had spoken with President Trump to make sure that states are not competing with the federal government for the crucial supplies.
“I’m hoping and anticipating that the president’s going to live up to the commitment that he made to me when I raised this issue with him,” Baker said. "You can’t bid against us if you expect us to go out and buy this stuff.
Globe correspondent Jeremy C. Fox and Nick Stoico, and Matt Rocheleau, Dugan Arnett, Gal Tziperman Lotan, Priyanka Dayal McCluskey, and John Hilliard of the Globe staff contributed to this report.