Recently, a boy in Texas died of an infection with what headlines are calling a “brain-eating amoeba.” Unlike other catchy nicknames for little-known life forms (remember murder hornets?), this one accurately describes the organism in question. It’s an amoeba, and in rare cases it does actually feed on human brain tissue.
What actually causes this infection?
Naegleria fowleri is an amoeba, a single-celled creature that’s bigger than a virus or a bacterium, but still microscopic. N. fowleri lives in warm water, so you might find it in hot springs or summertime lakes in warm parts of the world. Its usual food is probably other microscopic creatures like bacteria, but it’s also able to feed on human brain tissue.
How does it get into your brain?
We don’t have to worry about swallowing N. fowleri — our stomachs would digest it. It’s also not transmitted by surfaces or coughs. No, it seems to require that water containing the amoeba go directly up our nose.
This is why it’s so rare, because how often do you put warm water up your nose? Most cases of N. fowleri infection can be traced to swimming or splashing in warm water; but if you use a neti pot to rinse the inside of your nose, follow the CDC’s recommendations to boil or filter the water, or purchase distilled water, to be sure it’s amoeba-free.
How does it kill you?
Once the amoeba makes it up your nose, it finds the nerves that connect your pharynx to your brain and begins to feed on the olfactory bulbs, a part of your brain that is involved in smelling. Often, a loss of smell and taste is one of the first signs of infection.
From the olfactory bulbs, it proceeds to the rest of the brain where it can be deadly.
Once your immune system notices that your brain is being eaten, it sends immune cells and cranks up the inflammation response. Your brain is being eaten, and it’s also being attacked by your own immune system. (Inflammation is the immune system trying to help, but there can also be collateral damage. The result is a condition called primary amoebic encephalitis, or PAM.
Most known cases of PAM have been fatal, but there are some experimental treatments that seem to have been successful.
Is it coming for me next?
The good news about N. fowleri infection is that it’s very rare. There have only been 145 reported cases in the U.S. since the 1960s. In some years, there are zero; in others, just a few. There are only very rare cases in Australia.
Because it prefers warm water, cases are more common in warm parts of the U.S., like Texas and Florida. Most of the northern half of the U.S. hasn’t recorded any cases at all.
In everyday life, there’s no specific thing to do to prevent it. When somebody contracts the amoeba from a swimming hole or splash pad, usually there were thousands of people who swam there with no ill effects. We don’t know why some people are susceptible, and according to the CDC we don’t have a reliable way of testing water to say whether it’s safe or not.
The best thing you can do is to reassure yourself that it’s rare, and make sure that you’re following safety guidelines if you’re intentionally putting water up your nose.