It wasn’t only Mr. Biden; it was also the people around him. Ron Klain, a longtime top adviser and former Biden chief of staff, opposed a travel ban on Jan. 28, a few days before it was announced, calling it “premature.” Other Biden advisers were also dismissive. On Jan. 30, Biden confidant and coronavirus adviser Zeke Emanuel told CNBC viewers to “take a very big breath, slow down, and stop panicking and being hysterical.” The virus will “go down as spring comes up.”

Throughout February, Mr. Biden’s lieutenants kept minimizing the threat. In a Feb. 6 op-ed, Biden coronavirus adviser Irwin Redlener wrote that a global pandemic was “not very likely” and predicted the chances of “getting a severe, potentially lethal form of the Wuhan virus is negligible.” On Feb. 11 Mr. Klain again played down the likelihood that Covid would become “a serious epidemic.” “The evidence suggests it’s probably not that,” he said. Two days later, Mr. Klain tweeted, “We don’t have a COVID-19 epidemic in the US but we are starting to see a fear epidemic.”

Suggesting in a Feb. 20 interview that there’d been “an overreaction,” Dr. Emanuel again suggested “warm weather is going to come and, just like with the flu, the coronavirus is going to go down.” Then on Feb. 24 House Speaker Nancy Pelosi urged tourists in San Francisco to “come to Chinatown.” Mr. Klain echoed her three days later, saying people should not be dissuaded by “needless fears about coronavirus.” He added that everyone “should tonight go down to Chinatown in their city and buy dinner or go shopping.”