MORE POWERFUL THAN TERRORIST ATTACK(2)

The virus has killed more than 1,000 people, infected over 42,000 and reached some 25 countries, with the WHO declaring a global health emergency.

Addressing scientists at the first international conference on combating the virus earlier on Tuesday, Tedros warned that the virus was a "very grave threat".

"Viruses can have more powerful consequences than any terrorist action," he told reporters later.

About 400 scientists were taking part in the two-day international meeting in Geneva called to review how the virus is transmitted and possible vaccines against it.

"We are not defenceless," Tedros said, adding: "If we invest now ... we have a realistic chance of stopping this outbreak."