The Marburg or "bleeding eye" virus in Rwanda has killed at least 15 people so far. Rousettus aegyptiacus, a fruit bat, is considered its natural host. It also spreads through human-to-human contact. It's marked by high fever, headache and muscle aches. Patients may develop haemorrhagic manifestations, including fresh blood in vomit and faeces and bleeding from nose, eyes or ears.