New York City’s renowned restaurant and nightlife industries — global destinations and trendsetters for generations — awoke Monday to a devastating new world, finding themselves all but shut down in an open-ended battle against a microscopic threat.

From storied steakhouses to humble corner saloons, owners, waiters, chefs and bartenders arrived for work on Monday as if for a funeral, hours after Mayor Bill de Blasio ordered them to close by Tuesday morning.

“We’re completely lost,” said Odalys Rivera, pouring coffee at a new taqueria, Cena, which opened in Brooklyn’s Windsor Terrace just last year and is the if-we-can-make-it-here dream of Ms. Rivera’s brother and her cousin, the owners.

The shutdown promises to affect all strata of the industry, from the owners and their celebrity chefs to the waiters and waitresses, bar-backs and busboys, who effectively are facing layoffs and may be unable to pay their rent.