Beyond the Cleveland rally on Tuesday night that was canceled, the Biden campaign canceled a planned event on Thursday in Tampa, Fla. He has additional public events scheduled in Chicago and Miami in the coming week.
Mr. Biden told NBC News that he was following the recommendations of the Centers for Disease Control and Prevention.
“I’m looking to the C.D.C. for advice,” he said. “If you notice in here, we did a fist bump, we didn’t shake hands. Well, I think that we’re going to follow the recommendations of the experts, and if they conclude that there shouldn’t be big indoor rallies, then we’ll stop big indoor rallies. We’re going to do whatever they say.”
After Mr. Sanders concluded a rally in St. Louis on Sunday, he engaged in his typical physical contact with top surrogates and supporters. He and the half-dozen people who spoke before him onstage all put their arms around one another for photographs, and Mr. Sanders then shook hands with several people who had been standing behind him during his 44-minute speech.
Later Monday, Mr. Sanders added to his schedule a hastily arranged news conference at the Westin hotel near a Detroit airport to discuss how he would respond to the coronavirus if he were president.
Asked what precautions he was taking to keep himself healthy, Mr. Sanders gestured to the table where he sat with prominent surrogates, who included Dr. Abdul El-Sayed, the former Detroit public health director, and Deborah Burger, a nurse who is the president of the National Nurses United union, which backs his campaign.
“Well, I’m surrounded by medical personnel,” he said. “I’m running for president of the United States, and that requires a whole lot of work.”
Reid J. Epstein reported from Dearborn Heights, and Thomas Kaplan from Detroit.