I don't know for sure what is the case with this but thrre is species of amoeba that is known to causing lethal damge to the brain (can't remember name because I read that 4 years ago).
This parasite I am talking about leaves in water and can be transmitted to humans to humans through infected water also I think some birds get infected too.
Although there are not many known cases of it, it is known that the disease it causes leads to death most of the time and doesn't have symptom, but in some cases, in the end of the second week after it infects, the person can some times bleed from the nose but most of the time it is very late to take any measures.
The people recovering from these have some problems with moving parts of their body and in some other cases they have problems like memory loss and such.