SAN JUAN, Puerto Rico — Sequoia Mack and her friend flew from Baltimore to Puerto Rico Sunday night hoping to hit some clubs and celebrate her 21st birthday. Instead their night consisted of walking to a gas station to buy water — the only establishment they could find open amid an islandwide lockdown.

Puerto Rico, a sun-kissed U.S. territory of 3.2 million people, has taken some of the most extreme measures in the nation as it tries to fight the spread of the coronavirus.

Gov. Wanda Vázquez on Sunday imposed a 9 p.m. to 5 a.m. curfew that will run through month’s end and ordered all nonessential businesses closed.

Large swaths of the city were eerily empty. In Old San Juan, most restaurants and all the noisy lively bars usually blaring salsa music were closed. And the port, often a riot of cruise-ship passengers and traffic, was a ghost town.

Under the governor’s decree, only restaurants that offer take-out, grocery stores, pharmacies, banks and a few other “essential” businesses can stay open.

But theaters, museums, bars, malls, gyms, jewelry stores — most things that might attract tourists — are shuttered.

Tourists are getting turned away from beaches and the popular El Yunque National Forest by police.