The decision to hand Pence authority — and responsibility — for what could be the most significant crisis of Trump's three years in office reflects both the president's aversion to bucks stopping on his desk and his level of trust in a partner he had viewed with skepticism at the beginning of their relationship.

Trump announced Pence's new responsibilities Wednesday night, a day after returning from a brief sojourn to India , during which the public was jolted to the reality of a dangerous pandemic reaching American shores.

While he was gone, senior officials at the Centers for Disease Control and Prevention (CDC) raised serious alarms about the likelihood that the virus would spread here, and both Republican and Democratic senators voiced concerns that the administration's request for emergency funding was inadequate.

Trump on Wednesday continued to downplay the threat the virus poses as he defended his administration's initial response to the outbreak. At the same time, he demonstrated little knowledge of his team's planned response, and contradicted the dire warnings voiced by senior public health officials just the day before.

"The risk to the American people remains very low," Trump said in a press conference. "We're very, very ready for this — for anything."

That message stood in stark contrast to what Nancy Messonnier, who heads the CDC's National Center for Immunization and Respiratory Diseases, told reporters on Tuesday

"It’s not a question of if this will happen, but when this will happen and how many people in this country will have severe illnesses," Messonnier said. "Disruption to everyday life might be severe."

Trump's efforts to brush off the threat of the coronavirus are a deliberate repeat of the Obama administration's early mistakes in its efforts to combat growing public anxiety over the spread of the Ebola virus in the summer of 2014.

Then, the administration lost control of its "keep cool" approach after two American missionaries who had contracted Ebola in Liberia were brought back to the United States for treatment, a decision private-citizen Trump sharply criticized at the time in dozens of tweets

Now, Trump has insisted that the coronavirus will not spread significantly throughout the U.S., even though the nation has already treated at least 58 patients and his own experts are warning about a significant outbreak.

"We're ready to adapt and we're ready to do whatever we have to as the disease spreads, if it spreads," Trump said Wednesday.

Minutes later, CDC Deputy Director Anne Schuchat said: "We do expect more cases, and this is a good time to prepare."

In a deeply worrying new development, news broke while Trump was speaking on Wednesday that the first case of coronavirus with an unknown connection to any existing case in the U.S. had been diagnosed at the University of California-Davis hospital in Sacramento County.

Since being named Trump's vice presidential nominee almost four years ago, Pence has played the faithful lieutenant, the ever-deferential servant who never breaks ranks from a president whose tone and temperament is so fundamentally different from his own.

On Wednesday, he once again praised Trump as he took control of the response.

"From the first word of an outbreak of the coronavirus, the president took unprecedented steps to protect the American people from the disease," he said.

Pence is a former governor who dealt with a serious HIV outbreak in his home state of Indiana while in office, so he knows something about outbreaks and the critical role the federal government plays in response.

But the coronavirus is not like Ebola or HIV: Those viruses are very difficult to transmit, requiring physical contact with a bodily fluid of an infected person. The coronavirus transmits much more easily, through droplets emitted by coughs or sneezes. And neither Ebola nor HIV can live long on surfaces; it is unclear how long the coronavirus can survive outside a human body.

Public health officials — including some of those most closely involved in the Obama administration's response to the Ebola outbreak — have also warned that the virus's spread inside the United States is virtually inevitable.

"It’s inevitable that it will be spread within the US," former CDC director Tom Frieden told The Hill in an interview. "Now how widespread it is, how much harm it causes, that only time will tell."

Now, Pence faces two potential outcomes: If the virus does not spread within the country, he will win credit for leadership in a time of crisis, Trump's thanks for confronting a threat to the ticket's reelection hopes this year, and potentially a major chit toward his own hopes of running for president in what appears to be an increasingly crowded field of Republicans vying for a post-Trump nomination in 2024.

For years rumors have circulated that Trump is interested in or considering dumping Pence from the ticket during his 2020 reelection campaign. Trump has denied those rumors , and so has Pence. Yet in handing him oversight responsibility for the coronavirus, the president has given his No. 2 the chance to prove himself fireable.

Meanwhile, early signs point to a widespread outbreak, one that has already leapt from China to South Korea, Italy and Iran. Add in the troubling case near Sacramento, unconnected to any previously known transmission chain, and millions of Americans could be at risk of coming down with the virus.

Trump has set expectations for stopping a readily and easily transmissible virus almost impossibly high. It will be up to Pence to meet those expectations — or to face the consequences of a mercurial boss determined to avoid responsibility.

— This report was updated on Feb. 27 at 5:48 a.m.