The symptoms—bleeding, fever, fatigue, headaches, vomiting—look like Ebola, but that virus has been ruled out as the cause of a hemorrhagic fever that has killed 10 and afflicted at least 51 in South Sudan.
33 of the cases tested all came back negative for Ebola, and the WHO said the mystery illness responds rapidly to supportive care and does not appear to spread from person to person. (The transmission mechanism is not yet established.) Tests for Marburg virus and Crimean-Congo fever came back negative as well.
5 samples did test positive for the mosquito-borne virus O'nyong-nyong. But that doesn’t add up yet, either, as O'nyong-nyong is non-fatal and doesn't cause bleeding.