"We have to keep our guard up," Sylvie Briand, Head of Epidemiology at the UN's health agency, told at a two-day conference at the Pasteur Institute in Paris.
Briand said the situation in Guinea, one of the three West African states where Ebola has killed more than 11,000 people, left her "deeply concerned." Briand warned against hopes that a line could be drawn under the epidemic. "I am afraid there could be another wave that could spread to neighboring countries," she said.
Liberia was recently declared Ebola-free but Sierra Leone and Guinea remain vulnerable to a resurgence of the lethal virus.