White House officials expressed growing alarm on Tuesday about the coronavirus outbreak in New York City, advising people who have passed through or left the city to place themselves in a 14-day quarantine.

Officials warned that the outbreak could reach its peak in New York City much sooner than expected and said they had begun treating the region as a coronavirus hot zone, akin to areas of China and Europe overwhelmed by the virus.

About 60 percent of the new cases in the country were in the New York City metropolitan area, and the infection rate was eight to 10 times greater than other parts of the country, officials said at a briefing with the White House Coronavirus Task Force.

“Anyone in the New York metropolitan area who has traveled: Our task force is encouraging you to monitor your temperature, be sensitive to symptoms, and we are asking anyone who has traveled out of the New York City metropolitan area to anywhere else in the country to self-isolate for 14 days,” Vice President Mike Pence said.