"I think we're getting a better sense (of the scope of the outbreak) as the days go by," Anthony Fauci, the head of the infectious diseases unit at the National Institutes of Health, said on NBC's "Meet the Press."
"Unfortunately, that better sense is not encouraging because we're seeing community spread," he said.
He encouraged those most at risk from coronavirus to limit travel.
"If you're a person with an underlying condition and you are particularly an elderly person with an underlying condition you need to think twice about getting on a plane, on a long trip, and not only think twice, just don't get on a cruise ship," Fauci said on "Meet the Press."
Fauci said that in addition to efforts to try to contain the spread of the virus, it was important to start thinking about how to mitigate the impact as more and more Americans fall ill."They call it 'social distancing,' but it's common sense stuff," he said. "You don’t want to go to a massive gathering, particularly if you are a vulnerable individual.