The risk of a global spread and impact of the coronavirus is now "very high", the highest level of alarm, but containment is still possible, the World Health Organization (WHO) said on Friday.
WHO chief Tedros Adhanom Ghebreyesus said it would be a "big mistake" to switch from a public health strategy of containment to mitigation, where authorities accept the virus is spreading.
In recent days, 24 cases had been exported from Italy to 14 countries and 97 cases from Iran to 11 countries, Tedros said.
"Our epidemiologists have been monitoring these developments continuously. We have now increased our assessment of the risk of spread and the risk of impact of COVID-19 to 'very high' at global level," he told a news briefing.
He added: "We do not see evidence as yet that the virus is spreading freely in communities. As long as that is the case we still have a chance of containing this virus."
China's 329 reported cases in the past 24 hours was the lowest there in more than a month, he said.
"We are on the highest level of alert and the highest level of risk assessment in terms of spread and in terms of impact. But that is not in order to alarm or scare people," said Dr. Mike Ryan, executive director of WHO's emergencies program.
"People need to take a reality check now and really understand an all-of-government, an all-of-society approach is needed," Ryan said.
"We have been dealing with this virus for two months and I think this is a reality check for every government on the planet - wake up, get ready...You have a duty to your citizens, you have a duty to the world to be ready."
The WHO mission to Iran has been delayed due to "issues with getting flights and access to Iran right now", Ryan said, but the government of the United Arab Emirates was helping to facilitate access and delivery of supplies.
"The UAE is helping with this. We hope Sunday at the earliest, if not by Monday, we should have people on the ground," Tedros said.
Ryan said Nigeria, whose first case was confirmed as an Italian man who arrived from Milan, had "well-tested mechanisms for dealing with these dangerous pathogens", citing experience with Lassa fever and cholera.
The most populous African country has expanded its influenza diagnostics and the same labs can now do COVID diagnosis, he said.
"That is not to say that there are not risks. Nigeria is a vast country with a huge population, and it has many vulnerable people, especially in the north and lots of refugees and many others.
"So it is disappointing to see the disease arrive, but it's also heartening to see that the disease was picked up and a single importation was confirmed quickly. And that isolation and other activities have already begun," Ryan added.
Mexico has become the second country in Latin America to report cases: "There is no reason to think (the virus) would act differently in different climate settings," said Dr. Maria van Kerkhove, a WHO epidemiologist.