The number of new Ebola cases has increased for the first time in 2015 in all three affected countries, the WHO's latest weekly figures show,
There were 124 new confirmed cases in the week to 1 February - 39 in Guinea, five in Liberia and 80 in Sierra Leone.
The increase will raise questions over whether efforts to contain Ebola have been successful, correspondents say.
More than 8,500 people have died in the outbreak, but recently numbers of cases have been decreasing.
BBC.COM