MONROVIA, Liberia >> The U.N. chief has appointed a new head of the emergency mission responding to West Africa’s Ebola outbreak.

A statement from Ban Ki-moon’s office says Peter Jan Graaff of the Netherlands will work closely with David Nabarro, the U.N.’s special Ebola envoy, as officials try to end an epidemic that has claimed more than 10,000 in the three hardest-hit countries: Liberia, Guinea and Sierra Leone.

The U.N. Mission for Ebola Emergency Response was established last September. Outgoing head Ismail Ould Cheikh Ahmed has been appointed as special envoy to Yemen.

Graaff had been serving since October as the U.N.’s Ebola crisis manager in Liberia, which has recorded more Ebola deaths than any other country. Liberia’s last known Ebola patient died on March 27.