"We are asking the American public to work with us to prepare with the expectation that this could be bad," Messonnier said.
"I had a conversation with my family over breakfast this morning. And I told my children that while I didn't think that they were at risk right now, we, as a family, need to be preparing for significant disruption of our lives," she said.
Those measures could include school closings, workplace shutdowns and canceling large gatherings and public events, she warned.
"I understand this whole situation may seem overwhelming and that disruption to everyday life may be severe, but these are things that people need to start thinking about now," Messonnier said.
So Americans need to do things like start making plans to care for their children should schools and day care centers close, she said. They should talk to their employers about how they could work from home. And they should find out if there might be a way to get medical care remotely, such as through telemedicine, Messonnier said.
She stressed that the current risk remains low. Almost all the cases that have occurred in the United States have been among travelers who got infected overseas. In addition, there's always the chance that the coronavirus could begin to subside as the spring and summer arrive.
Infectious disease experts say that 80% of infections are mild, no more severe than the common cold.
So far, there have been 14 confirmed cases of the coronavirus illness COVID-19 in the U.S. and 40 other cases among people who were repatriated to the U.S. after being on the Diamond Princess cruise ship. An additional three cases are among people who were repatriated from Hubei province in China, where the respiratory virus emerged months ago.
Hand-washing with soap and water continues to be a top recommendation to protect against the virus, since the abrasiveness of soap helps remove infectious particles from the hands. Experts say that commonly worn surgical masks aren't very effective protection. A heavy-duty mask called an N95 respirator is considerably better protection, but it is uncomfortable to wear and can make breathing more difficult.
The CDC has advised against nonessential travel to China and South Korea, countries that have seen the highest numbers of cases.
But because there are so many unknowns, state and local officials and average Americans need to be prepared, Messonnier said.
"I continue to hope that in the end we'll look back and feel like we were overprepared. But that is a better place to be in than being underprepared," she said.
World Health Organization Sees Progress
Meanwhile, despite worrisome new outbreaks in Iran, Italy and South Korea, the coronavirus disease called COVID-19 is not currently a pandemic, the World Health Organization said Monday.
In fact, there are some encouraging trends, especially in Hubei province, where most of the cases have been reported.
The epidemic there appears to have plateaued in late January and is continuing on a good trajectory. Dr. Bruce Aylward led a WHO trip to China with a scientific delegation that just concluded. On Sunday, he told reporters in Beijing that trend is real.
Aylward said that he'd spoken to a researcher in Wuhan who is testing potential drugs to treat COVID-19, "and when I asked him what challenge they're finding in trying to implement the trial, he said the single biggest one is recruiting new patients ... because of the drop in cases."
That's a good kind of problem. The message from China is that it's not hopeless, he says. It is possible to control this disease.
"Now we're starting to see countries like Italy take extremely aggressive actions," Aylward said. "What China has demonstrated is you have to do this, and if you do it you can save lives and prevent thousands of cases of what is a very difficult disease."
Getting the public's full cooperation to do the simplest tasks is a reason for the success.
"Believe it or not, the most valuable thing the whole population can do is wash its hands, continually," he said. Other useful measures include avoiding crowds, as you'd find in schools and large gatherings.
But restricting travel is not on Aylward's list of useful actions.
"You don't have to lock down cities is the big message from China, in fact," he said.
The WHO scientific delegation's task was to learn what worked in China and to spread the word. But even during their brief trip, the disease was making serious inroads in South Korea, Iran and Italy. As of Monday morning, South Korea had reported 763 cases, Iran had reported 43 cases — including eight deaths — and Italy added 48 cases to bring its national total to 124.
"There is a lot of speculation about whether this increase means that this epidemic has now become a pandemic," said WHO Director General Tedros Adhanom Ghebreyesus at a news conference in Geneva.
There have been 14 cases of the virus diagnosed in the U.S., all in people who traveled recently to China or their close contacts, according to STAT. Another 39 U.S. residents have been infected in other parts of the world before being repatriated and quarantined.
Assigning that label isn't simply a matter of whether a disease is on multiple continents, but whether it's out of control and doing significant damage. Those are decisions that WHO makes before declaring that a disease is a pandemic. The term was last used for the H1N1 flu virus that struck in 2009, sickening more than 60 million in the U.S. alone and killing some half a million worldwide.
"Does this virus [that causes COVID-19] have pandemic potential?" Tedros asked rhetorically. "Absolutely it has. Are we there yet? From our assessment, not yet."
There's still time for countries to get in front of it. The WHO's top priorities are to protect health care workers, to protect vulnerable people such as those who are sick and elderly, and to protect vulnerable countries.
Even the advanced nations of Europe have work to do, since their hospitals are pretty full these days with flu patients. Those beds might be needed for coronavirus patients.
If the spread of the coronavirus in Europe can be slowed until the end of flu season, that "will free up significant capacity of the health system," said Dr. Michael Ryan, executive director for the WHO's Health Emergency Program. "So even slowing down the virus by a month or six weeks has a massive positive benefit."