The new coronavirus has been declared a global emergency by the World Health Organization, as the outbreak continues to spread outside China.
"The main reason for this declaration is not what is happening in China but what is happening in other countries," said WHO chief Tedros Adhanom Ghebreyesus.
The concern is that it could spread to countries with weaker health systems.
At least 213 people have died from the virus in China.
The WHO said there had been 98 cases in 18 other countries, but no deaths. Most cases have emerged in people who have travelled from the Chinese city of Wuhan, where the outbreak began.
However, there have been eight cases of human-to-human infection - in Germany, Japan, Vietnam and the United States.
Speaking at a news conference in Geneva, Dr Tedros described the virus as an "unprecedented outbreak" that has been met with an "unprecedented response".