RABAT, Morocco -- The international medical organization Doctors Without Borders is sounding the alarm over the outbreak of the Ebola disease in West Africa as some 20 new deaths have been reported.

The World Health Organization said Monday that the latest figures show 567 cases with 350 deaths in Guinea, Liberia and Sierra Leone.

Their figures show most of the deaths are in Guinea, but the growth of new cases appears to be higher in Sierra Leone.

Doctors Without Borders, known by its French initials MSF, said Monday that the outbreak will require a "massive deployment of resources" by governments and aid agencies to bring under control.

This Ebola outbreak is the most deadly ever. The virus has no cure and causes internal bleeding and organ failure, spreading through contact with infected people.