People walk past a billboard encouraging people suffering from symptoms linked to Ebola to present themselves at a health facility for treatment in Freetown, Sierra Leone, Thursday, Aug. 7, 2014. While the Ebola virus outbreak has now reached four countries, Liberia and Sierra Leone account for more than 60 percent of the deaths, according to the World Health Organization. The outbreak that emerged in March has claimed at least 932 lives. (AP Photo/ Michael Duff)
The spread of Ebola remains "intense" in most of Sierra Leone even as things have improved somewhat in the two other countries hardest hit, the World Health Organization says.