The World Health Organization is due to announce the end of the two-year Ebola outbreak on Thursday, when Liberia is expected to get the all clear.

The announcement in Geneva will "mark 42 days since the last Ebola cases in Liberia were tested negative," the UN agency said in a statement, after Guinea and Sierra Leone were previously declared free of the virus. 

The announcement was previously scheduled for Friday, and no reason was given for the change.