In a joint statement from WHO's director-general, deputy director-general and regional directors, what has been learned and what reforms need to be made were suggested, including making outbreak prevention a global priority.

"We can mount a highly effective response to small and medium-sized outbreaks, but when faced with an emergency of this scale, our current capacities and systems - national and international - simply have not coped," the statement read.

Among the lessons and reforms, WHO plans to form the Global Health Emergency Workforce, establish a Contingency Fund, to remain vigilant and take threats seriously.

"We do not know when the next major outbreak will come or what will cause it," WHO wrote. "But history tells us it will come. This means investing domestically and internationally in prevention and in essential public health systems for preparedness, surveillance and response, which are fully integrated and aligned with efforts to strengthen health systems, and included in the scope of development assistance for health."

In a situation report released by WHO on April 15, WHO said there were 25,791 suspected Ebola cases in Guinea, Liberia and Sierra Leone with 10,689 deaths.