GENEVA/LONDON (REUTERS) - The Ebola epidemic is still spreading in Guinea, Sierra Leone and Liberia and the number of cases in West Africa will exceed 9,000 this week, the World Health Organisation (WHO) said on Tuesday, projecting there may be between 5,000 and 10,000 new cases a week by the beginning of December.

The death toll so far in the outbreak, first reported in Guinea in March, has reached 4,447 from a total of 8,914 cases, WHO Assistant Director General Bruce Aylward said.

While there are signs that rates of infection are slowing in some of the worst-hit areas, Aylward said the disease has now reached "more districts, counties and prefectures" than it had a month ago, and said case numbers would continue to rise.

He stressed it would be "really, really premature" to read success into the apparent slowing numbers in some areas, noting that by the first week in December, WHO projections suggest there may be between 5,000 and 10,000 new cases a week.

"It could be higher, it could lower but it's going to be in that ball park," he told reporters from WHO's Geneva headquarters. "In certain areas were seeing disease coming down but that doesn't mean they're going to go to zero," he said.

The WHO has repeatedly said Ebola cases are under-reported in the three hardest-hit countries, and that understanding the scale and pace of the outbreak is crucial to stopping it. "We adjust for the numbers reported," Aylward said.

The WHO multiplies the numbers from Guinea by 1.5, from Sierra Leone by 2 and from Liberia by 2.5 to get a more accurate picture, he said.

The published data could also be misleading because the number of known deaths is less than half the number of cases, but that gave a false impression, Aylward said.

The actual mortality rate is about 70 per cent, a figure that was consistent across the three worst-hit countries, he said.