World Health Organization has revealed that two people have fallen ill with Ebola in Guinea after two weeks with no new confirmed cases of the disease in West Africa.
WHO spokeswoman Margaret Harris told a United Nations (UN) briefing in Geneva that one case was in Forecariah, western Guinea, and appeared to be linked to a previously known chain of infection, while the other was in the capital Conakry.
Ebola transmission is considered to be over once a locality has gone 42 days without a new case of the disease. The other two countries that were worst hit by the epidemic were Liberia, which was declared transmission free on 3 September, and Sierra Leone, which is counting down another 22 days until it is clear.
"On the bumpy road we keep talking about, the high risk of recurrence, once again we are navigating a few bumps. Of course we didn't want it, but we did expect it. Guinea hadn't got to the stage where we were looking at 42 days," said Harris.
Even after that period, Ebola may lurk in the population. This month a study showed the semen of male survivors can harbour the virus for nine months, while a British nurse has fallen critically ill again 10 months after recovering from Ebola.
The medical toolkit for tackling Ebola has been transformed in the past few months by the success of a trial vaccine, which is now used to treat each new case and their contacts who may also be at risk from the highly contagious virus.
But Harris said that the trial comes to an end in mid-November, potentially putting a question mark over the use of the vaccine beyond that date.