Naegleria fowleri is an ameba (single-celled living organism) that lives in soil and warm fresh water, such as lakes, rivers, and hot springs. It is commonly called the “brain-eating ameba” because it can cause a brain infection when water containing the ameba goes up the nose. The first symptoms usually start about 5 days after infection, but they can start within 1 to 12 days. Symptoms may include headache, fever, nausea, or vomiting. Later symptoms can include stiff neck, confusion, lack of attention to people and surroundings, seizures, hallucinations, and coma.