The National Gallery of Art will not be open for its 80th anniversary next week and probably won’t welcome visitors to its galleries until mid-April. Meanwhile, the Smithsonian museums also remain closed, even as four more nonprofit museums in Washington prepare to reopen this week.

Closed to the public since Nov. 21, the NGA had been working toward a March 17 reopening, but Director Kaywin Feldman informed staff Monday that it would not open before mid-April.

“We continue to base our reopening decisions on the best available guidance from the CDC, health experts and other available metrics,” Feldman wrote in a staff email. “We continue to consult closely and coordinate with the Smithsonian Institution as we develop our reopening plans to maintain consistency across the federal museums. We will let you know as soon as we have more information regarding a new reopening date.”

The decision comes as health officials in Washington, Maryland and Virginia reported more than 1 million infections in the region since last March. Nearly half of the infections were reported in December and January, according to officials. More than 17,500 of those infected have died.

Despite the number of infections, Hillwood Estate, Museum and Gardens reopened on Tuesday. The National Museum of Women in the Arts reopens on Wednesday, Glenstone’s outdoor installations on Thursday and the Phillips Collection on Saturday. The Museum of the Bible and the International Spy Museum reopened in January.

The Smithsonian expects to reopen in phases but has not announced dates, a spokeswoman said. After closing in March, the Smithsonian reopened the National Zoo and the National Air and Space Museum’s Steven F. Udvar-Hazy Center in Chantilly on July 24, followed by the Smithsonian American Art Museum, the National Portrait Gallery, the National Museum of African American History and Culture, and the Renwick Gallery on Sept. 18. The National Museum of American History and the National Museum of the American Indian welcomed back visitors on Sept. 25.

The National Gallery reopened the ground-floor galleries of its West Building on July 20, but closed them Nov. 21 after infections in the region spiked. The Smithsonian followed on Nov. 23.

In recent weeks, NGA guards have raised concerns about coming back to work without being vaccinated. Many of them are older Black men who are at a higher risk for contracting covid-19; they have repeatedly asked gallery officials to offer them the vaccine before requiring them to return to work.

Several guards, who spoke on the condition of anonymity to speak about internal matters because they feared retaliation, said their supervisors raised the issue with museum leaders but did not have answers. Feldman addressed the topic at the end of her memo.

“We all know people who have been vaccinated and I am told by health officials that the numbers of available vaccines will increase substantially over the next two months,” Feldman wrote.

In an email to The Washington Post on Monday evening, Feldman said the health and safety of the staff and visitors have been “our guiding concern.”

“After watching the increase of covid cases locally and nationally, we closed the Gallery to the public in November. Likewise, as we have observed the steep decrease in cases over the last weeks, we had hoped that we could reopen in March. Over the past few days, we decided it would be prudent not to open in March based on guidance we are receiving from experts and the latest data on infections,” she said.

The NGA’s sculpture garden reopened Feb. 14 and continues to welcome visitors.