Conveying its most heightened level of alarm to date, the Centers for Disease Control and Prevention on Tuesday said Americans should begin preparing for a coronavirus pandemic that could disrupt their daily routines, including work and school.

During a telephone press briefing, Dr. Nancy Messonnier, director of the CDC's National Center for Immunization and Respiratory Diseases, said that given the level of "community spread" of the disease in South Korea, Italy and Iran, that it was no longer a question of if, but of "when and how many people in this country will have severe illness."

She added: “We are asking the American public to prepare for the expectation that this might be bad.”

"Community spread" is when the source of the infection is not known.

She said the CDC was currently "operationalizing" its pandemic plans, which included ensuring that hospitals and health care workers would have sufficient supplies, and urged people to begin preparing themselves. She said those with children should contact their schools about dismissal or closure plans in the event of a serious outbreak, and that businesses should begin discussing with their employees about working from home.

"I understand that this may seem overwhelming but these are things people need to start thinking about now," she said.

Messonnier added that she herself had spoken to her own children this morning, telling them that, "We as a family need to be preparing for significant disruption of our lives."

One of the complications of modeling outbreak scenarios is that researchers still do not know whether the coronavirus will be seasonal like influenza and other viral respiratory illnesses, she said.

Citing her 25 years of experience at the CDC, she added: "If you had asked public health officials what they feared as an expectation, it was something exactly like this."

The federal agency's message comes roughly two months after the virus was first reported in central China. Known officially as COVID-19, the coronavirus has infected nearly 80,000 people in 37 countries and led to at least 2,600 deaths.

The cases in the United States have been relatively limited to date, which federal officials have credited to early containment measures, including border restrictions and airport screenings. As of Tuesday, the CDC reported 57 confirmed cases, 40 of which were infected passengers repatriated from the Diamond Princess, a luxury cruise ship docked off Yokohama, Japan that had been described as a "petri dish" for the virus.

While there has been evidence that infection appears to be slowing in China, public health experts have been concerned over the rapid surge in cases in other countries in Asia and Europe. South Korea on Tuesday said it now had 893 cases, the second most in the world. On Tuesday, the Health Ministry of Iran said that its deputy health minister, Iraj Harirchi, who was leading the country's effort to contain the coronavirus, had become infected himself. Iran now has nearly 100 cases and 15 reported deaths.

And portending an eventual outbreak across Europe, Italy has been battling a outbreak in its northern region, with more than 300 cases and 10 deaths. At least 50,000 people in 10 towns have been in lockdown.

But in spite of the grim statistics, the World Health Organization as recently as Monday resisted calling the disease a pandemic. Meanwhile, President Donald Trump, who is visiting India, said on Tuesday that the coronavirus was "under control" in the U.S. and that it would not seriously affect the global economy. On Monday, Wall Street posted its most dismal performance in two years. Stocks and bond yields tumbled again following Tuesday's CDC announcement.

Dr. Ali Khan, the CDC's former director of the Office of Public Health Preparedness and Response, told Gothamist that the agency's warnings of a pandemic was weeks overdue.

"We are currently in the midst of a pandemic," he said. "The real issue has been what is going to be the severity of this pandemic."

He said the data has suggested that the fatality rate from the disease lies between 2 to 4 percent, representing a "substantial number of people" who could eventually die.

Khan, who is currently a dean of the College of Public Health at the University of Nebraska Medical Center, said the purpose of the CDC's message was to start engaging everyone in its strategy to contain and survive an outbreak. Rather than stirring panic, he said the intention was to get people to be "thoughtful."

Individual protections, he said, include refraining from touching your face, not smoking, and stockpiling necessities like medications for next couple of months.

"There’s preparedness at multiple levels that should be going on right now," he said.

Mayor Bill de Blasio's office did not immediately respond to a request for comment. As of Tuesday, there were still no confirmed cases in New York City. All told, there have been only seven suspected cases found in the city, none which were determined to be coronavirus.

Top scientists have been upfront about the unknowns of the latest disease, which resembles SARS but is thought to be more contagious. “How long does the current outbreak continue? Will it even disappear?” Dr. W. Ian Lipkin told Gothamist. “No one knows.”

Similarly, at a press briefing on Tuesday, Dr. Bruce Aylward, a researcher who led a World Health team who recently visited China, acknowledged that the level of preparation has not been adequate for the latest coronavirus.

"The main question is are we ready? No. You’ll never be ready," he said. "That’s the reality. You’ll never be as ready as possible."