NEW YORK, N.Y. – From its location in a Washington studio to podiums placed 6 feet apart, CNN's handling of Sunday's Democratic presidential debate illustrated how much the world had changed since the last time Joe Biden and Bernie Sanders met onstage.

The coronavirus epidemic dominated preparation for the two-hour debate and was the sole subject of the first 40 minutes of discussion.

Sunday's session stood in sharp contrast to the food-fight atmosphere of the Feb. 25 debate hosted by CBS, when Biden and Sanders were among seven candidates onstage. Still, both candidates highlighted their differences, and they had some spirited exchanges.

Originally set for the Arizona Federal Theatre in Phoenix, CNN and the Democratic National Committee decided on Tuesday that it would eliminate the audience and the press filing center to minimize the potential exposure of people to the virus. Two days later, they decided to move the event to a CNN studio in Washington.

“The overarching goal is to keep everyone safe and do the right thing,” said Sam Feist, CNN's Washington bureau chief.

The network set the two podiums for the candidates 6 feet apart in the studio to correspond with the recommendations by health authorities for social distancing. Surfaces in the studio were wiped down with disinfectant several times in the hours leading up to the debate.

Even before the debate, CNN panels of commentators sat notably farther apart from each other, and Chris Cuomo and Anderson Cooper were in separate studios. It set an example that other television networks are still coming to grips with: Earlier in the day, NBC's “Meet the Press,” ABC's “This Week” and “Fox News Sunday” all featured discussions with a moderator and four commentators crowded together around desks.

“It's an extraordinary moment in our history, and we are mindful of that and want to make sure that the tone of our debate and approach to the debate fits the moment,” Feist said.

When Biden and Sanders came into the studio, they greeted each other not with handshakes but with elbow bumps.

CNN's Jake Tapper and Dana Bash and Univision's Ilia Calderon — herself a replacement for Jorge Ramos, who stepped down after possibly being exposed to someone with the novel coronavirus — all addressed the epidemic from the start.

They started with more broad queries. Tapper asked, “What do you say to Americans who are confronting this reality?” Then they got more specific. Bash asked whether the candidates supported a national quarantine and whether the U.S. military should be deployed to help with the crisis. Calderon asked about the outbreak's economic impact and how immigrants in the U.S. illegally could be made to feel that it was safe to seek medical treatment.

When CNN's panel moved on from the topic, it felt more like a conventional debate. Biden and Sanders mixed it up in one exchange about cuts to entitlement programs that the moderators should have cut off more quickly.

Bash was quick to recognize when Biden provided the evening's headline, by committing to select a woman as his vice presidential candidate. She made sure to highlight that answer and asked Sanders for a specific response. She came back at him a second time, asking Sanders whether he would make a similar commitment. “In all likelihood, I will,” he said.

Tapper brought the debate full circle and ended the evening on a somber note, by asking each candidate whether he had a final message to people about what is happening with the coronavirus.

The moment emphasized the point Cooper had made moments before the event started: “We've never seen any debate quite like this,” he said.

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