The lawsuits, filed in state and federal court in New York, were one of the largest collective legal actions taken against hospitals since the pandemic began. In addition to the state Health Department, the defendants were Montefiore Medical Center and Westchester Medical Center.

The union, the New York State Nurses Association, said that at least eight nurses had died in New York State after contracting the virus at work, and at least 84 had been hospitalized. The union has more than 42,000 members.

In court papers, nurses described receiving one N95 mask to use for a week and being denied virus testing at their own hospitals. Some nurses who tested positive for the virus were required to return to work after seven days, half the 14-day quarantine period recommended by health officials, the union said.

[Coronavirus in New York: A map and the case count.]

Ambulance calls in N.Y.C. have dropped sharply.

Mayor Bill de Blasio said on Monday that there were 3,485 medical-emergency calls to 911 on Saturday, many fewer than on an average day in 2019, before the coronavirus outbreak began.

Calls have fallen more than 50 percent since a peak in late March, when there were more than 7,000 calls in a single day, more than on Sept. 11, 2001.

But with the city reporting 363 new deaths on Sunday, Mr. de Blasio warned that it was far too soon to lift lockdown restrictions on business and public life in New York.

In that vein, he announced that all large gatherings and events for June, including the Puerto Rican Day Parade and the Pride March, had been canceled. The two events draw millions of people to the city’s streets each summer.