Mali has now become the sixth West African country to be affected by the outbreak, although Senegal and Nigeria have since been declared virus-free by the WHO.
The WHO has three experts in Mali evaluating its ability to cope with Ebola and will send at least four more over the next few days, spokeswoman Fadela Chaib said.
With porous borders, countries neighbouring Guinea, Sierra Leone and Liberia are on high alert for possible imported cases of the virus, says BBC Africa health correspondent Anne Soy.