The World Health Organization convened outside experts Tuesday to fast-track promising tests, drugs and vaccines to help slow the outbreak of a new virus that emerged in China that has killed more than 1,000 people and spread to two dozen other countries.

The new coronavirus was only identified late last year in the Chinese city of Wuhan and there are no licensed drugs or vaccines. Diagnostic tests have been developed by several laboratories, but there are no rapid tests available. More than 300 scientists were expected to dial in remotely to the two-day meeting in Geneva that began Tuesday.

To date, the virus has infected more than 43,000 people and has killed 1,007, with 99% of the cases found in China. Two dozen other countries have reported 393 cases of the virus, with one death in the Philippines.

WHO director-general Tedros Adhanom Ghebreyesus said the epidemic was "very much an emergency'' for China but also "one that holds a very grave threat for the rest of the world.'' He said there was still a window of opportunity to shut down the outbreak.

At least 60 million people in central China are in a government-ordered lockdown aimed at halting the spread of the virus and health authorities around the world are racing to track down the contacts of infected people and isolate confirmed cases.

In Japan, more than 3,700 people remain quarantined aboard a cruise ship in Yokohama, south of Tokyo, after dozens of passengers and crew tested positive for the virus.

"It's hard to believe that just two months ago, this virus _ which has come to captivate the attention of media, financial markets and political leaders _ was completely unknown to us,'' said Tedros.

The U.N. health agency said there were still many critical but unanswered questions about the virus, including what animals it came from, how exactly it is spread between people and how best to treat infected patients.

"To defeat this outbreak, we need answers to all those questions and more,'' Tedros said.

Experts say it could still be months or even years before any approved treatments or vaccines are developed.