"This outbreak could still go in any direction," the WHO's director-general, Tedros Adhanom Ghebreyesus, told a briefing in Geneva.
At the end of a two-day meeting on research and innovation into measures to tackle the new viral outbreak, Tedros welcomed the energy and enthusiasm of scientists starting work.
He added that a WHO-led advance team that traveled to China earlier this week had made "good progress" on the composition and scope of its work.