Naegleria While naegleria is super-rare, it’s super-serious, so awareness is key. Merely swimming or diving in a warm freshwater lake or river is enough to expose you to this potentially deadly amoeba, which causes primary amebic meningoencephalitis (PAM), similar to bacterial meningitis. Initial symptoms include headache, fever, nausea and vomiting, progressing to confusion, stiff neck, seizures and hallucinations. PAM can cause death within five days, and the fatality rate is over 99 percent. Because of this, people who are infected should seek medical attention as soon as possible. There are effective treatments for naegleria, but only if it’s caught early. The best way to prevent these infections is to avoid swimming in these waters altogether.