The World Health Organization (WHO) has declared the coronavirus outbreak is now a global public health emergency.
WHO director-general Tedros Adhanom Ghebreyesus said on Friday (NZ time) the concern wasn't what was happening in China, but in countries less prepared to deal with the deadly virus.
"We don't know what kind of damage this virus could do if it were to spread to a country with a weaker health system."
He said it was not a vote of no confidence in China's ability to control the outbreak.
"We would have seen many more cases outside China by now and probably deaths if it were not for the Government's efforts and the progress they have made to protect their own people and the people of the world...
"The speed with which China detected the outbreak, isolated the virus, sequenced the genome and shared it with WHO and the world are very impressive. So is China's commitment to transparency and to supporting other countries... In many ways China is actually setting a new standard for outbreak response."
There have now been more than 7800 cases in China - 99 percent of all infections - and 98 in other countries, the vast majority of which have been linked to travel to Wuhan, where the virus originated. All 170 deaths linked to the disease have been in China.
There have been eight cases of human-to-human transmission outside of China - in Germany, Japan, Vietnam and the US.
"So far we have not seen any deaths outside China, for which we must all be grateful," said Dr Tedros. "Although these numbers are still relatively small compared to the number of cases in China, we must all act together now to limit further spread."
But Dr Tedros said there was "no reason for measures that unnecessarily interfere with international travel and trade".
"We call on all countries to implement decisions that are evidence-based and consistent. WHO stands ready to provide advice to any country that is considering which measures to take."
Dr Tedros recently travelled to China to speak with President Xi Jinping and "see for himself" what was happening.
"I have never in my life seen this kind of mobilisation," he said, saying it would "reverse the tide" of the outbreak.
"It's the President himself who is leading this effort. The day we arrived the Prime Minister was in Wuhan, and all the relevant ministers. This is impressive... I believe they will control this outbreak."