Nearly 6,400 people have now died from Ebola, the World Health Organization said Wednesday, amid a ballooning case load in Sierra Leone.

The UN health agency

reported 17,942 cases of the deadly virus across eight countries as of December 7, resulting in a total of 6,388 deaths -all but 15 of them in Guinea, Liberia and Sierra Leone. Sierra Leone meanwhile reported 397 new cases during the week of December 7 - three times as many as Liberia and Guinea combined, WHO said.

The country now counts a total of 7,897 Ebola cases, including 1,768 deaths, according to Wednesday's tally.

A full third of the new cases, or 133 of them, were reported in the capital Freetown, at the heart of the ongoing surge in cases seen in the west of the country.