Late Summer is Deadly Lake Amoeba Season

Late Summer is Deadly Lake Amoeba Season

Every year, several people die from an infection by a water-borne amoeba Naegleria fowleri. Its latest victim is a 16 year-old girl who became infected after swimming in a Florida river. This amoeba likes warm, stagnant water, which is why cases often rise during late summer and early fall. The combination of warmer waters and more swimmers means that the risk of infection is far greater than during the rest of the year.
The amoeba enters the victim's body through the nose, when infected water is pushed up into the sinus cavities. This happens during swimming, particularly swimmers who jump into the water or dive down too deep. The amoeba attaches itself to the olfactory nerves and uses these as a highway to gain access to the brain.
Survival rates for N. fowleri infections are shockingly low: about 3% of sufferers survive the illness, according to the CDC. This is partly because many people are not taken to the hospital until it's too late, as the early symptoms of the disease are relatively mild. Within a week after infection, the early symptoms include headaches, vomiting, stiff joints and neck, and a fever - similar to what you would expect from the flu or a bad cold.
One warning sign that could indicate a N. fowleri infection is cognitive disorders and odd behavior. Sufferers may lose their balance, report hallucinations, experience muscle spasms, seizures, or uncontrollable movements, and say or do unusual things. This happens because the amoeba, once it finds its way to the brain, begins eating neurons, typically starting with the frontal lobe.
By this time, the body's own defensive reaction has the unfortunate side effect of causing meningitis - swelling of the membranes which surround the brain - which can be fatal in and of itself. The swift progression of the disease is similar to that of bacterial meningitis, which it is often initially diagnosed as.
(Obviously if any of these symptoms occur in conjunction with a high fever it's time to see a doctor immediately, regardless of whether or not the patient has been swimming recently!)
There is no effective treatment for N. fowleri infections. Although it is an extremely rare disease, the only known way to prevent it is to use nose clips while swimming in non-chlorinated water, and to avoid warm, still water (like lakes and ponds) during the late summer months. (This is good advice in general, given the ambient level of fecal coliform bacteria in stagnant warm water during the summer months!)