Geneva: The weekly Ebola cases in the three most affected countries -- Guinea, Liberia and Sierra Leone -- rose for the first time this year, according to the latest tally released Wednesday by the World Health Organization(WHO).

Last week, 124 new cases of Ebola were registered in these three countries-- 39 of them were in Guinea, five in Liberia and 80 in Sierra Leone.

"Weekly case incidence increased in all three countries for the first time this year," the WHO said in its latest update.

The WHO warned that some people continue to engage in unsafe practices, thus increasing their risk of becoming infected or infecting others.

It said that the virus continues to spread geographically in Guinea, with 39 cases in the most recent week. Only 30 cases were registered in the prior week in Guinea.

Sierra Leone registered 80 new cases last week, when only 65 cases were registered in the previous week.

The WHO said that "significant challenges" were confronting authorities seeking to limit the spread of the virus.

To date, 22,495 confirmed, probable or suspected cases have been registered in the three hardest-hit African nations, and of those 8,981 people have died.