In his most sweeping effort yet to contain the coronavirus, Governor Cuomo announced that New York State would restrict most gatherings of more than 500 people. Soon after, Mayor de Blasio declared a state of emergency in New York City.

Across the state, schools, hospitals, nursing homes and public transit will be exempt from the restrictions on gatherings, which will go into effect for most venues today at 5 p.m., Mr. Cuomo said.

[Read our live coverage of the coronavirus outbreak in the New York area.]

The announcement was an especially heavy blow to the theater industry, a crown jewel of New York City’s tourist trade, and came after cultural institutions including the Metropolitan Museum of Art said they would suspend visits and performances.

As of yesterday afternoon, New York State had at least 328 confirmed cases of the coronavirus, the governor said. The city, which had 95 confirmed coronavirus cases as of yesterday, could have 1,000 by next week, the mayor said.

Here’s what else you should know:

In his news conference yesterday, Mr. de Blasio cited the potential for major job losses. He also noted the possibility of large-scale evictions of renters, mass business closings and even food shortages.