The ultimate test of Donald Trump's presidency may be a virus whose name he misspelled in a tweet, claiming that it is not nearly as "bad" as the media is making it out to be.

And Trump's press conference Wednesday did not reassure public health experts that he now has any greater grasp of the peril that coronavirus, which causes the disease COVID-19, represents to the American people, the economy and his presidency.

At the press conference,Trump made no mention of the current case toll, which yesterday rose to 60 infections in the United States – 45 of those cases are American passengers from the Diamond Princess cruise ship who have been flown back to the U.S.

He did not say that the latest case – in a person from rural Northern California who hadn't traveled to a coronavirus hotspot or come in contact with anyone who had – was the first suggestion that the coronavirus may now be circulating at least in one community in the U.S., a sign that the pool of infections may be growing.

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"As most of you know," Trump said, "the level that we've had in our country is very low. Those people are getting better, or we think that in almost all cases they are getting better. We have a total of 15. We took in some from Japan. You heard about that because they are American citizens. They're in quarantine, and they're getting better, too."

For a public health expert who recognizes the magnitude of the threat that COVID-19 represents, the president's performance was terrifying.

"It was absolutely unhinged," epidemiologist Gregg Gonsalves of Yale University said Thursday. "He had no command of facts, he was rambling. It was astounding."

The president's remarks climaxed days of mixed messages that spooked financial markets, sending the stock market sinking into correction territory. On Thursday, U.S. stocks suffered their biggest point loss in history. And any drop in the Dow poses a threat to a president whose reelection hopes hinge largely on a strong economy.

"If the coronavirus epidemic materially affects U.S. economic growth it may increase the likelihood of Democratic victory in the 2020 election," Goldman Sachs analyst Ben Snider and colleagues wrote in a report out Wednesday night.

The epidemic also gives Trump's Democratic opponents an opportunity to showcase their leadership skills in times of crisis.

Former New York Mayor Michael Bloomberg on Wednesday aired a 30-second television ad excoriating Trump for his response to coronavirus and highlighting his own management of events that occurred during his tenure, including the aftermath of 9/11.

"(President Trump's press conference) was absolutely unhinged ... (Trump) had no command of facts, he was rambling. It was astounding."

And political analysts say the situation could help former Vice President Joe Biden , who has staked his candidacy on his competence and electability. Biden can point to his time in the White House during another public health emergency: the Ebola epidemic of 2014.

Even the U.S. Chamber of Commerce, which has been supportive of Trump, urged the president to appoint a "czar" to coordinate the government's response "to protect Americans from the Coronavirus." Saying the country needed "clear accountability and data-based guidance so the public and American businesses can take the proper precautions to mitigate the impact."

Later that day, Trump appointed Vice President Mike Pence to run the coronavirus task force that has been meeting since the virus emerged, reportedly infuriating Alex Azar, the secretary of Health and Human Services.

Trump praised Pence for his public health policies as governor of Indiana, saying they were the envy of other states. Gonsalves takes issue what that characterization, saying Pence's record in Indiana was a public health disaster, stripping thousands from the Medicaid rolls and opposing a needle-exchange program for opioid abusers that might have prevented 250 people in the grip of addiction from also becoming infected with HIV.

With COVID-19, Pence will have his hands full. Just two months after China reported the first cases to the World Health Organization on Dec. 31, WHO has confirmed more than 80,000 cases and 3,000 deaths from the virus. Since then, nearly 40 countries are reporting cases, and the virus is still spreading. Eighty percent of the cases are mild, experts say, but that makes them more difficult to detect.

Ten days ago, not a single case had been reported in Iran. Since then Iran has reported 129 cases with 18 deaths, centered in the holy city of Qom, a popular site for pilgrims traveling for thousands of miles to visit its temples and shrines. Two cases have been reported in Pakistan, which promptly closed its border with Iran.

Germany reports that the virus has begun spreading undetected from person to person at the community level. Brazil yesterday reported its first case, the first in Latin America. Saudi Arabia suspended travel to Mecca and Medina. Japan began instituting social controls, urging people to avoid congregating and whenever possible to work from home. The country said it would close its schools until April.

Researchers estimate that every person infected with COVID-19 spreads the virus to two to three others. After 10 generations, each lasting about a week, a single individual can infect more than 3,500 people, who may or may not be symptomatic and may be capable of infecting others, Dr. Michael Osterholm, director of the Center for Infectious Disease Research at the University of Minnesota, and writer Mark Olshaker say in The New York Times .

The death rate appears to be approximately 2%, higher than the flu, which causes from 25,000 to 69,000 deaths each year. On Wednesday, Trump expressed astonishment that the flu kills so many people. "That was shocking to me,'' Trump said of the annual flu toll. "So far, if you look at what we have with the 15 people … they're recovering.''

But that may not be the case for long. Given the 2% death rate, if 1 of every 10 people in a city of 11 million inhabitants comes down with the new virus, as many as 20,000 may die. And in a global pandemic, the death toll may be far worse.

"We don't have a specific mitigation strategy," says Nancy Messionnier, director of the Centers for Disease Control and Prevention's National Center for Immunization and Respiratory Diseases at a recent briefing at the Aspen Institute. Until there's a vaccine, she said, "it will be social distancing. If you're sick, stay home. Wash your hands."

Messonnier predicted that in the U.S. "disruption to everyday life might be severe" as the virus begins spreading within communities, impacting businesses, prompting schools to close and flooding hospitals with an onslaught of patients. WIth SARS, the last coronavirus outbreak two decades ago, hospitals were anything but a refuge. Health workers were hit hardest.

And the crisis is just beginning, Messonnier said. "This is a disease we didn't know existed [just a few] weeks ago."

Even working at breakneck speed, it will take researchers at least a year to craft a vaccine capable of slowing its spread, Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases said Wednesday at the Trump press conference -- after Trump himself said that a vaccine would be developed "fairly rapidly."

The first safety trials of a prototype vaccine are slated to begin within two months. After those trials are complete, bigger studies, requiring hundreds or thousands of people, will be required to prove that the vaccine is effective. If the initial prototype vaccine doesn't work, two candidate vaccines are also waiting in the wings. But vaccine development will take time.

"Is there a risk that this will turn into a global pandemic?" Fauci said at the Aspen Institute. "Absolutely, yes, there is."

Funding is needed now, not just to ramp up the response but to sustain it, globally and locally.

"This is a critical moment," says John Auerbach, president of the Trust for America's Health, a nonpartisan public health advocacy group.

The administration has proposed $2.5 billion to counter the outbreak, but the amount includes just $1.25 billion in new money and would draw off $535 million in federal funds meant to fight Ebola.

"We think that's a lot," Trump said.

But Senate Minority Leader Chuck Schumer countered with a request for $8.5 billion and Trump signaled a willingness to spend more.