Daniel Radcliffe heard he had the new coronavirus from his makeup artist.

“We’d just done the matinee,” Mr. Radcliffe said, referring to his March 10 performance in “Endgame” at the Old Vic theater in London. “I was getting my hair done for the evening show, and our hair and makeup guy, Rob, turned around and said, ‘You’ve got coronavirus, apparently. My niece just texted me.’”

A rogue tweet, posing as BBC breaking news, had blown up. There were inevitable jokes playing on the role that made him famous (“Harry Potter and the Deathly Viruses”) and new hashtags (#ExpectoCoronus), and a typically wry quip from Mr. Radcliffe himself. “I think it’s because I look ill all the time,” he told an Australian radio station.

But the rush to identify the first celebrity infected with the coronavirus would continue. This was fake news.

Still, a scheduled face-to-face interview with Mr. Radcliffe three days later seemed inadvisable, given the rapidly shifting ground. Instead of meeting at a favorite diner — Mr. Radcliffe wouldn’t reveal the name to preserve his privacy — we had a Skype video call at the appointed hour from his dressing room. “We’re on the cutting edge here,” he said, just as his features pixelated and froze.

Dressed in a black T-shirt and hoodie, he talked a little like a runaway train, sentences running into sentences. “What’s annoying about it is, like, if things keep going the way they are going, I might well get it at some point,” he said, chuckling at the absurdity of the situation. “I don’t know what that makes me feel, to be honest. It’s just, like, odd. I read somewhere that they said I was a perfect person to do it with because I don’t have social media, so I can’t see it and respond immediately.”

Asked about his dressing room, Mr. Radcliffe gamely held up his monitor for a guided tour. The panorama included a rumpled bed; a handmade card from Grant Shaffer, the husband of his co-star Alan Cumming; and a pile of fan mail. How much does he receive a day?

“About a foot, probably,” he said. He tries to respond to it all.

Over the course of 75 minutes, Mr. Radcliffe spoke about his abiding love for “The Simpsons,” his upcoming turn as a “very posh, stupid prince” in the movie version of “Unbreakable Kimmy Schmidt” and his psychological response mechanism to the tenacious characterization of child actors as nightmares.

“Knowing that is what people think about young actors made me counteract that to the point where you could be quite rude to me and I would not notice,” said Mr. Radcliffe, who is now 30. “I would be so paranoid that you could say whatever you liked.” It had, he added, given him an excess of sympathy for celebrities like Justin Bieber.

It has also fueled Mr. Radcliffe’s determination to put Harry Potter behind him and be judged for his body of work. “I am always going to feel that I got incredibly lucky, but at the same time I do believe you can justify it a bit retroactively by working really hard,” he said.

In the bleakly comic and relentlessly claustrophobic “Endgame,” a play by Samuel Beckett, he plays the submissive Clov to Mr. Cumming’s cantankerous and blind Hamm. As with Beckett’s other work, it’s a existential disquisition on the meaning of life, in which a codependent couple take shelter from a senseless world.

The play, which opened in late January, became more pertinent as the weeks passed. “It’s a funny time to be doing a play about the end of the world,” Mr. Radcliffe said. A line repeated several times — “Something is taking its course” — had started eliciting knowing and nervous laughs of recognition, he said.

As it happens, “Endgame” is not the only project of Mr. Radcliffe’s to find uneasy parallels with the current global crisis. “Miracle Workers: Dark Ages,” a TBS comedy by the writer Simon Rich in which Mr. Radcliffe stars with Steve Buscemi, is set in an era defined by iniquity and stasis.

A plot twist in the Season 2 finale, scheduled for March 31, involves a suspected outbreak of the Plague.

On the advice of his producers, Mr. Radcliffe had recently begun avoiding contact with his fans — a steep learning curve for a chatty and personable actor who considers selfies par for the course. Inculcated by his father to always initiate a handshake, he has to work hard to abandon an ingrained habit.

“It’s just a lot of feeling like you are being incredibly rude,” he said. “Sometimes you’ll go to do an elbow thing and somebody will look at you, as if, ‘Come on, are we really doing that?’ and I have to reply, ‘Yes, I’m sorry, I’m really paranoid about it, I don’t want to get sick and spread that around.’”

At the gym in his building he had become fastidious about cleaning the equipment down with a bottle of disinfectant. “Today I was just on the treadmill, but I did a full spritz beforehand,” he said. (Workouts may have ended at this point, given the restrictions on a lot of gyms.)

But Mr. Radcliffe also knows these small adjustments are a mere inconvenience compared to the larger catastrophe facing the theater industry. He considers the Old Vic, where he also starred in “Rosencrantz and Guildenstern Are Dead,” a second home.

“One has to assume that this is literally what a government is for, and they have to step in and help people,” he said.

For more than a decade Mr. Radcliffe has used the stage to build a post-Harry Potter career, starting memorably with Peter Shaffer’s homoerotic classic, “Equus,” about a teenage boy who blinds six horses. “The young wizard has chosen wisely,” Ben Brantley wrote in The New York Times when the play arrived on Broadway.

That was followed by the musical “How to Succeed in Business Without Really Trying,” which Mr. Radcliffe said was one of his favorite projects.

In all, he has starred in seven theater shows and at least 10 movies since graduating from Hogwarts.

Anxiety about life after Potter also exacerbated Mr. Radcliffe’s reliance on alcohol. He stopped drinking in 2013, helped by his parents and friends as well as other actors, and said the mind-set that keeps him from alcohol is helping him navigate the coronavirus anxiety today.

“To really know and understand what it means to take something one day at a time is an attitude that really helps across life,” he said. “When you first stop drinking, you have to be convinced that you can ever have fun again.”

A knock at his dressing room door announced the arrival of his dinner: chicken breasts and fries from Nandos, a popular restaurant chain specializing in peri peri chicken. Mr. Radcliffe wasn’t sure how many more meals he’d eat at the Old Vic. “You’re aware that every show could be the last,” he said.

Mr. Radcliffe was back onstage on Saturday, to a crowd, but by last Sunday evening, the Old Vic had become the first theater in London to close, albeit voluntarily. In order to save the theater from financial crisis, producers of “Endgame” asked ticket holders to consider accepting a video link to the show in lieu of a refund.

Even before being relieved of his obligations, Mr. Radcliffe was eager to to be reunited with his girlfriend, the actress Erin Darke, in New York. “Honestly, I am desperately trying to get back,” he said. “I’m very much aware that this is not the main tragedy of this global pandemic, but I do not want to be not with her through whatever it is that’s happening.”

Mr. Radcliffe met Ms. Darke when he was filming “Kill Your Darlings,” in which he plays the Beat poet Allen Ginsberg, and they will celebrate their eighth anniversary in a few weeks. When they are not working, they watch movies or play board games, and are well equipped for quarantine.

“I’m going to make us sound ancient, but we play cribbage,” Mr. Radcliffe said, visibly blushing on Skype. They also enjoy a game called Welcome to Your Perfect Home. It is about urban planning. “I can’t describe it without making it sound intensely dull, but it’s very addictive,” Mr. Radcliffe said.

Has the relationship changed him in any way? The actor considered the question. “I’ve definitely gotten better at prioritizing life stuff as well as work stuff,” he said, and paused. “To be honest, I still have a long way to go.”

It was time to eat, and then nap before his penultimate performance in “Endgame.” To sign off, Mr. Radcliffe came in close to his computer’s camera and lifted his arm for a virtual elbow bump from across the pond.

“Hopefully I’ll be over there in a few weeks,” he said. “We shall see.”