The Ebola outbreak in West Africa has killed 2,461 people, half of the 4,985 infected by the virus, World Health Organisation Assistant Director General Bruce Aylward said on Tuesday.
"Quite frankly, ladies and gentlemen, this health crisis we're facing is unparalleled in modern times," Aylward told a news conference in Geneva. "We don't know where the numbers are going on this."
He said previous forecast that the number of cases could reach 20,000 no longer seemed a lot, but the number could be kept within the tens of thousands with "a much faster reponse".