The “whole world needs to be on alert” to fight the coronavirus, the head of the World Health Organization Health Emergencies Programme has said.
Dr Michael Ryan praised China’s response to the deadly outbreak, saying: “The challenge is great but the response has been massive.”
The WHO will meet on Thursday to discuss whether the virus constitutes a global health emergency.
The Chinese city of Wuhan is the epicentre of the outbreak.
But the virus has spread across China and to at least 16 countries globally, including Thailand, France, the US and Australia.
More than 130 people have died in China and close to 6,000 have been infected.
The WHO’s Dr Ryan said an international team of experts was being assembled to go to China and work with experts there to learn more about how the disease is transmitted.
“We are at an important juncture in this event. We believe these chains of transmission can still be interrupted,” he said.
The organisation’s director general Tedros Adhanom Ghebreyesus, who visited China this week, said most people who contracted the virus were suffering only “milder symptoms”, but about one in five had severe effects such as pneumonia and respiratory failure.
He said the WHO “deeply regrets” referring to the worldwide risk from the virus as “moderate” instead of “high” last week.
Hundreds of foreign nationals are being evacuated from Wuhan, where the virus first emerged, with Japan, the US and the EU among those repatriating their citizens.
Australia plans to quarantine its evacuees on Christmas island, 2,000km (1,200 miles) from the mainland.
British Airways has suspended all flights to and from mainland China, as the UK’s Foreign Office warned against “all but essential travel” there.
Several other airlines have taken similar measures. United Airlines and Cathay Pacific are restricting flights, while Lion Air – one of the region’s biggest airlines – is stopping flights to China from Saturday.
Cathay Pacific has also suspended in-flight trolley services, changed some aspects of its meal offer, and stopped giving out hot towels, pillows, blankets and magazines in an effort to prevent the virus spreading.