GENEVA (Reuters) - China’s coronavirus outbreak poses a “very grave threat for the rest of the world” and should be viewed as “Public Enemy Number 1”, the head of the World Health Organization (WHO) said on Tuesday.

WHO director-general Tedros Adhanom Ghebreyesus urged countries to step up measures to detect and contain the virus, especially in at least 30 countries with weaker health systems, where it could “create havoc”.

The virus has been named COVID-19, for coronavirus disease 2019, with no geographical association, he said.

Tedros, referring to some governments’ counter-terrorism measures, said: “To be honest, a virus is more powerful in creating political, economic and social upheaval than any terrorist attack.

“A virus can have more powerful consequences than any terrorist action. If the world doesn’t want to wake up and consider this enemy virus as Public Enemy number 1, I don’t think we will learn from our lessons,” he said.

China has reported 42,708 confirmed confirmed cases, including 1,017 deaths, Tedros said, noting that there were fewer than 400 cases in 24 other countries with one death.

WHO began a two-day meeting, where it appealed for sharing virus samples and speeding up research into drugs and vaccines.

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“The first vaccine could be ready in 18 months. So we have to do everything today using the available weapons to fight this virus while preparing for the long term using the preparations for the vaccines,” Tedros said.

“With 99% of cases in China, this remains very much an emergency for that country, but one that holds a very grave threat for the rest of the world,” he told more than 400 researchers and national authorities, including some taking part by video conference from mainland China and Taiwan.

Tedros, speaking to reporters on Monday, referred to “some concerning instances of onward transmission from people with no travel history to China”, citing cases this week in France and Britain. Five British nationals were diagnosed with the coronavirus in France, after staying in the same ski chalet with a person who had been in Singapore.

“The detection of this small number of cases could be the spark that becomes a bigger fire. But for now it’s only a spark. Our objective remains containment,” he said.

Hong Kong residents evacuated from a residential building where a man and woman confirmed with coronavirus live tested negative for the virus, health authorities said on Tuesday, easing concerns of a cluster of the outbreak in the Chinese-ruled city.

Many questions remain about the origin of the virus, which emerged at a wildlife market in the central Chinese city of Wuhan in December, and is spread by people in droplets from coughing or sneezing.

“We hope that one of the outcomes of this meeting will be an agreed roadmap for research around which researchers and donors will align,” Tedros told the meeting.