Abbas Dulleh, Associated Press
In this Saturday Nov. 8, 2014 file photo, Ebola health care workers bury the body of a person suspected of dying of Ebola virus on the outskirts of Monrovia Liberia.

MONROVIA, Liberia — The U.N. peacekeeping mission in Liberia says one if its staffers has contracted Ebola, bringing to four the number of its members who have come down with the disease during the worst outbreak on record.

U.N. spokesman in New York Stephane Dujarric said the ill staffer is from Liberia. The patient was immediately transferred to an Ebola treatment unit, according to a statement from the mission.

The statement said the mission was taking "all necessary measures to mitigate any possible further transmission — both within the mission and beyond." These steps included isolating at-risk staffers and decontaminating vehicles used by the patient.

The World Health Organization says Liberia has recorded 3,384 deaths during the Ebola outbreak — more than any other country.

Two of the U.N. staffers who earlier contracted Ebola have died.

AP writer Cara Anna contributed from New York.