The death toll from the coronavirus outbreak has risen to 170, and a confirmed case in Tibet means it has reached every region in mainland China.
Chinese health authorities said there were 7,711 confirmed cases in the country as of January 29.
Infections have also spread to at least 15 other countries.
Various countries have implemented evacuation and quarantine plans for nationals wanting to return from China, where the outbreak began in the city of Wuhan.
Russia has decided to close its 4,300km (2,670-mile) far-eastern border with China in an attempt to stop contagion.
WHO Director-General Tedros Adhanom Ghebreyesus named Germany, Vietnam and Japan, as places where people had caught the virus from others who had visited China.
“Although the numbers outside China are still relatively small, they hold the potential for a much larger outbreak,” he said, adding that human-to-human transmission was a concern.
More people have now been infected in China than during the Sars outbreak in the early 2000s, but the death toll remains far lower. Sars, also a coronavirus, caused acute respiratory illness.
Researchers are racing to develop a vaccine to protect people from the virus. One lab in California has plans for a potential vaccine to enter human trials by June or July.
Voluntary evacuations of hundreds of foreign nationals from Wuhan are under way to help people who want to leave the closed-off city and return to their countries.
The UK, Australia, South Korea, Singapore and New Zealand are expected to quarantine all evacuees for two weeks to monitor them for symptoms and avoid any contagion.
Australia plans to quarantine its evacuees on Christmas Island, 2,000km (1,200 miles) from the mainland in a detention centre that has been used to house asylum seekers.
Singapore is setting up a quarantine facility on Pulau Ubin, an island north-east of the city-state’s mainland.
In other developments:
* Six thousand people on board a cruise ship in Italy were barred from disembarking after a Chinese passenger was suspected of having coronavirus; however initial tests have come back as negative
* Flights to take British and South Korean citizens out of Wuhan have both been delayed after relevant permissions from the Chinese authorities did not come through
* Two flights to Japan have already landed in Tokyo. Three passengers have so far tested positive for the virus, Japanese media report
* Around 200 US citizens have been flown out of Wuhan and are being isolated at a military base in California for at least 72 hours
Two aircraft are due to fly EU citizens home with 250 French nationals leaving on the first flight
Meanwhile, the BBC reports that India has confirmed its first case of the virus – a student in the southern state of Kerala who was studying in Wuhan.
