Sierra Leone has identified 28 high risk contacts in the country's north after a new Ebola case emerged in the West African nation last week.

National Coordinator of Office of National Security, Ishmael Tarawallie, said over the weekend that 109 contacts had been found, and three known contacts were missing.

Sierra Leone authorities Friday said swabs from a 22-year-old woman who died last week tested positive for Ebola. The case came a day after the World Health Organization declared the outbreak over in West Africa.

Tarawallie said preliminary reports show the woman sought outpatient medical treatment.

Nearly 4,000 people died before Sierra Leone was first declared free from transmission Nov. 7. Ebola has killed more than 11,300 people, mostly in West Africa, since this outbreak emerged in late 2013.