The US has declared a public health emergency over the spread of the coronavirus and said it would deny entry to any foreign nationals who have visited China in the past two weeks.
US citizens returning from Hubei province, where the outbreak started, will be quarantined for 14 days.
Almost 12,000 cases of the new virus have been confirmed, most of them in China, since it emerged in December.
More than 100 cases have been reported outside China, in 22 countries. On Friday, Beijing said the death toll had risen by 46 to 259 – all of them in China and 249 in Hubei.
In a public statement the US Health Secretary Alex Azar said US citizens returning from Hubei province would face 14 days of quarantine while those returning from other parts of China would be allowed to monitor their own condition for a similar period.
“Following the World Health Organization decision, I have today declared that the coronavirus represents a public health emergency in the United States,” he told reporters.
Citing the need to relieve pressure on authorities, he said that foreign nationals who had travelled in China in the past 14 days would be denied entry to the US.
“The risk of infection for Americans remains low and with these, and our previous, actions we are working to keep the risk low,” he added.
Another confirmed case in the US on Friday – in California – brought the number there to seven. Robert Redfield, director of the Centers for Disease Control and Prevention, said 191 people were under observation for the disease.
Earlier, it emerged that the number of new coronavirus cases worldwide had overtaken that of the Sars epidemic, which spread to more than two dozen countries in 2003.
There were around 8,100 cases of Sars – severe acute respiratory syndrome – during the eight-month outbreak. In total, 774 people were killed by Sars.
After weeks of hesitation, the World Health Organization (WHO) declared the virus a global health emergency on Thursday.