The World Health Organization (WHO) says there is a “window of opportunity” to stop the deadly new coronavirus becoming a broader global crisis.

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.

WHO briefing on Coronovavirus in Geneva:

Speaking at a technical briefing in Geneva, Dr Tedros praised the Chinese authorities for their response at the epicentre of the outbreak – the city of Wuhan, in the province of Hubei, where millions of people are on lockdown and severe transport restrictions have been imposed.

“There is a window of opportunity because of the high measures, the strong measures China is taking at the epicentre, at the source. So let’s use this opportunity to prevent further spread and control it,” he said, stressing that developed countries were failing to share data.

Dr Tedros also reiterated his call for countries not to impose travel and trade restrictions, saying 22 nations had officially reported such measures. He urged them to be “short in duration, proportionate” and reviewed regularly.

But Chen Xu, China’s ambassador to the UN in Geneva, said some restrictions went against the WHO’s advice.

Earlier, Sylvie Briand, head of WHO’s Global Infectious Hazard Preparedness division, said the outbreak “currently” was not a pandemic.

While more than two dozen nations have reported cases there have been no confirmations across Africa or Latin America. Twenty-seven cases of human-to-human infections have occurred in nine countries outside China, according to the WHO.

Dr Briand also stressed the importance of tackling unfounded rumours, saying they could be an “obstacle for good response and hamper effective implementation of counter-measures”.