10 Deadly Agents the CDC Works With

Primary Amoebic Meningoencephalitis (PAM)
Scared of swimming in lakes because of brain-eating amoeba? Don't be. Just hold your nose when you're jumping in. © John Lund/Drew Kelly/Blend Images/Corbis

Three words you never want to hear spoken together: brain-eating amoeba. But that's the ghoulishly glib name given to Naegleria fowleri, a mind-munching microbe that causes brain-destroying meningoencephalitis, a disease similar to bacterial meningitis. Its mortality rate -- more than 97 percent of its victims die, usually within days -- is matched only by its rarity: From 2004-2013, only 34 such infections were reported in the U.S. [source: CDC].

Although the amoeba lives in warm fresh water and soil all over the U.S., the infection only occurs when tainted water makes its way deep into the nose, as during irrigation with neti pots, religious head-dunking, or swimming or diving in lakes, rivers or underchlorinated swimming pools. Early symptoms, which kick in one to seven days after infection, resemble those of bacterial meningitis and can involve headache, fever, nausea or vomiting. Later, symptoms progress to stiff neck, confusion, hallucinations, balance difficulties, a tendency to pay less attention to people and environs, and seizures. Once symptoms appear, victims face a rapid downward plunge, and death follows within one to 12 days.

No treatment for PAM currently exists; nor do we have a way to test water for the amoeba that causes it [source: CDC]. In two reported cases, doctors achieved some success using brain-swelling management and miltefosine, an investigational breast cancer and anti-leishmaniasis drug. But all other cases resulted in death, so the value of this and other drugs remains unclear [sources: CDC; Jacobson].