A 15-year-old boy has died of Ebola in Liberia, the first death since the summer in a country that thought itself free of the virus.
Liberia's chief medical officer Francis Kateh said the boy, Nathan Gbotoe, died Monday in a hospital outside Monrovia where his father and brother are also being treated for Ebola.
Health officials say they're mystified by the reappearance of the virus. There are no known cases in the area, the family doesn't appear to have been in contact with any recent cases and Liberia's two neighbors, Guinea and Sierra Leone, have no known Ebola cases.
Close to 160 people who'd been in contact with the family are under watch, including 10 healthcare workers considered at high risk of infection because they treated the patients before it was known they had Ebola.
Liberia has been declared free of Ebola twice. The last known case was in July.
More than 28,000 people have been infected and more than 11,300 people have died of the virus since the outbreak was announced in March 2014. Of the three countries hardest hit, Sierra Leone was declared Ebola-free on Nov. 7 and Guinea started its own countdown to zero on Nov. 16 after its last case, a baby named Nubia, began her recovery.
Reuters and the Associated Press contributed to this report