This is called the “brain-eating amoeba” because it destroys brain tissue. It lives in warm lakes and rivers, and it can travel up your nose when you swim. Symptoms include headaches, fever, nausea, and vomiting. Later, it can cause stiff neck, seizures, and hallucinations. Most infected people die, but the disease is rare. Between 1962 and 2008 there were 111 reported cases in the U.S., mostly among young, healthy men.