Naegleria fowleri is an ameba (single-celled living organism) that lives in soil and warm freshwater, such as lakes, rivers, and hot springs. It is commonly called the “brain-eating ameba” because it can cause a brain infection when water containing the ameba goes up the nose. Only about three people in the United States get infected yearly, but these infections are usually fatal.
You cannot get infected from drinking water contaminated with Naegleria. You can only be infected when contaminated water goes up into your nose.
Symptoms usually start with severe headache, fever, nausea, and vomiting and progress to stiff neck, seizures, altered mental status, hallucinations, and coma.
Naegleria fowleri infects people when water containing the ameba enters the body through the nose. This typically happens when people go swimming, diving, or when they put their heads under fresh water, like in lakes and rivers. The ameba then travels up the nose to the brain, where it destroys the brain tissue and causes a devastating infection called primary amebic meningoencephalitis (PAM). PAM is almost always fatal.
Naegleria fowleri infections may also happen when people use contaminated tap water to rinse their sinuses by sending water up the nose. In very rare instances, people have gotten Naegleria fowleri infections from recreational water that didn’t have enough chlorine in it, such as pools, splash pads, or surf parks. There is no evidence that Naegleria fowleri can spread through water vapor or aerosol droplets (such as shower mist or vapor from a humidifier).
Recommended preventative steps include:
- Avoid jumping or diving into bodies of warm fresh water, especially during the summer.
- Hold your nose shut, use nose clips, or keep your head above water when in bodies of warm fresh water.
- Avoid putting your head under water in hot springs and other untreated geothermal waters.
- Avoid digging in, or stirring up, the sediment in shallow, warm fresh water. The amoebae are more likely to live in sediment at the bottom of lakes, ponds, and rivers.