Dr. Isabelle Nuttall, director of the World Health Organisation's global capacities, alert and response, said new numbers showed the outbreak is still hitting health workers hard despite precautions, with 2,700 medical workers infected and 236 dead, mainly because Ebola victims are most contagious around the time they die.
Nuttall said the focus of the world's efforts should remain on the countries where the outbreak has been spreading out of control: Liberia, Sierra Leone and Guinea.
"Our data shows that cases are doubling every four weeks," she told a news conference in Geneva.
Although the effects of the crisis are increasingly being felt beyond its epicentre in West Africa, until now two nurses in Dallas and a Madrid nursing assistant are the only ones known to have contracted Ebola outside the hot zone.
The death rate in the Ebola outbreak has risen to 70 percent and there could be up to 10,000 new cases a week in two months, the World Health Organization warned Tuesday.
Nuttall said Ebola cases were growing in Guinea's capital of Conakry but problems with data-gathering in Liberia, which has a significant under-reporting of Ebola cases in Monrovia, the capital, make it hard to draw any conclusions there.
It will take months before the outbreak is stopped, she said, adding that WHO has identified 14 African countries where being prepared and containing Ebola is a top priority.
Those countries are Benin, Cameroon, Central African Republic, Democratic Republic of the Congo, Gambia, Ghana, Guinea-Bissau, Ivory Coast, Mali, Mauritania, Nigeria, Senegal, South Sudan and Togo.
In Geneva, Newly-appointed U.N. High Commissioner for Human Rights, Zeid Ra'ad Al Hussein, says the "twin plagues of Ebola and ISIL" have been underestimated for too long.
At his first news conference since becoming the U.N.'s top human rights official last month, Zeid focused on the ``two monumental crises'' that he said would inevitably cost nations many billions to overcome.
"The twin plagues of Ebola and ISIL," he told reporters, using an acronym for the group, "both fomented quietly, neglected by a world that knew they existed but misread their terrible potential before exploding into the global consciousness during the latter months of 2014.''