The Sheraton Boston Hotel on Dalton Street notified people with reservations today that it's closing until at least June 26 and says they can rebook at the nearby Marriott Copley Place:

Thank you for choosing to stay with us at the Sheraton Boston Hotel. We are consolidating our hotel inventory in Boston and for this reason, as of March 27th, 2020 the hotel will be temporarily closed through June 26th, 2020, therefore all reservations during this time frame will be cancelled without penalty. Any advanced funds collected will be returned and Bonvoy points will be returned. If you booked through a third-party partner that has collected any deposits, please contact them directly. They have been notified of the hotel’s temporary closure.

The Marriott Long Wharf closed on March 12 after several dozen Biogen managers became infected with Covid-19 at a conference there.

Also shut: The Boston Harbor Hotel, through at least May 18, the Seaport Hotel, through at least April 21, the Omni Parker House, through May 18, and the Hyatt Regency, through May 10. The Mandarin Oriental is also closed, doesn't give a potential re-opening date.