Director-General Tedros Adhanom Ghebreyesus said the steps taken by China to fight the virus at its epicentre were the best way of stopping its spread.
Meanwhile, China's envoy to the UN in Geneva told nations not to over-react.
At least 427 people have died with more than 20,000 confirmed cases worldwide.
The WHO has declared a global health emergency over the outbreak but said the virus did not yet constitute a "pandemic" - the worldwide spread of a new disease. Officials say 425 people have died in China, one in Hong Kong and one in the Philippines.
About 80% of those who died were over the age of 60 and 75% of them had pre-existing health conditions such as cardiovascular diseases and diabetes, according to China's National Health Commission (NHC).
The new coronavirus causes severe acute respiratory infection and symptoms usually start with a fever, followed by a dry cough. Most people infected are likely to fully recover - just as they would from a flu.