OMAHA, Neb. (AP) — A doctor from the University of Nebraska Medical Center is back in West Africa to help respond to the ongoing Ebola outbreak.

Ali Khan left for Sierra Leone earlier this month to spend a month working with the World Health Organization.

Khan is the dean of public health at UNMC. He also spent six weeks in Sierra Leone beginning in January.

The Ebola outbreak has killed more than 11,200 people since last year, mostly in West Africa.

Over the past year, UNMC and the Nebraska Medical Center treated several patients infected with the Ebola virus and provided training to health care workers.