LONDON — On Broadway, theater doors are shut. In Milan, the Teatro alla Scala opera house is silent. In Paris, theaters including the storied Comédie-Française announced on Friday they were closing down temporarily, too.

Across the United States and across Europe, theaters and other cultural venues have drawn the curtains as authorities try to halt the spread of the coronavirus.

But on Friday afternoon, inside the National Theater in London, the show was going on. Dozens of people milled around in the foyer of the concrete building on the south bank of the river Thames, many of them with a drink in hand. They were about to go in and see “The Seven Streams of the River Ota,” Robert Lepage’s seven-hour saga about the repercussions of the atomic bombing of Hiroshima.

Tasha Kitcher, 22, said she wasn’t worried about sitting next to a stranger for such a long time. “We’re British,” she said, “so it’s, like, whatever.”