Naegleria fowleri is a microscopic, single-celled amoeba that lives in warm bodies of freshwater and soil. It can cause a rare, but usually fatal infection of the brain called primary amoebic meningoencephalitis (PAM) if water containing the amoeba enters the nose. Symptoms appear 2-15 days after infection and include fever, nausea, vomiting, and headaches. The infection progresses rapidly and usually causes death within 1-2 weeks. Diagnosis involves examining cerebrospinal fluid for the presence of the amoeba. Treatment options are limited and most patients do not survive even with drug therapy.