The warning comes at the start of huge declines in business for the tourism and entertainment sectors in New York City and the rest of the country. Bars and restaurants here will stop serving customers on-premises starting Tuesday, under a Sunday emergency order from Mayor de Blasio. Last week, Gov. Cuomo banned gatherings of more than 500 people as he declared a state of emergency, effectively shuttering Broadway, museums and stadiums. The U.S. has imposed severe travel restrictions on Europe and other countries.