German Chancellor Angela Merkel says the Ebola crisis in western Africa has shown the world in a painful way that a global catastrophe plan is needed to deal with future epidemic outbreaks.

Merkel told the World Health Assembly Monday that "the struggle (against Ebola) is only won if there are no new cases and if we have learned the lessons from this crisis: we should have reacted earlier."

The World Health Organization has been criticized for its slow response to early warnings about the Ebola outbreak.

More than 11,000 people have died from the outbreak since the first cases became public in rural Guinea in March 2014.

The assembly, which is the WHO's decision-making body, is attended by delegations of all WHO member states and meets annually in Geneva, Switzerland.