Naegleria fowleri ameba

Naegleria fowleri is an ameba (single-celled living organism) commonly found in warm freshwater bodies such as lakes, rivers, and hot springs as well as soil. In rare cases, it can cause a severe infection in the brain.

Naegleria fowleri grows best at higher temperatures up to 115°F (46°C) and can survive for short periods at higher temperatures.

Risk of Infection

Although Naegleria fowleri is commonly found in warm freshwater, infection is very rare.

According to the U.S. Centers for Disease Control and Prevention, 40 infections were reported across the entire U.S. from 2010 through July 2022. South Carolina has reported three cases from 2010 through July 2022.

While infections with Naegleria fowleri are rare, they occur mainly during the summer months of July, August, and September. Recreational water users should assume that Naegleria fowleri is present in warm freshwater across the United States and be aware that there is always a low-level risk of infection.

Most commonly, exposure results in the ameba dying before causing infection.

How you can prevent infection

The only certain way to prevent a Naegleria fowleri infection due to swimming is to refrain from water-related activities in warm, untreated or poorly treated water.

To reduce your risk:

• Avoid water-related activities in warm freshwater during periods of high water temperature and low water levels.
• Hold your nose shut, use nose clips or keep your head above water when taking part in water-related activities.
• Avoid digging in or stirring up sediment surrounding warm, fresh water.

How Infection Can Occur

Naegleria fowleri infection is caused by the ameba entering the brain through the nose.

For infection to occur, you must be swimming or participating in activities in water in which the ameba is present. Second, the ameba-containing water must reach your nasal cavity with enough force that the ameba can make its way to the brain.

On rare occasion, infection has been associated with swimming pools with inadequate levels of chlorine, as well as flushing sinuses with contaminated water.

Infection can usually be prevented by either holding your nose as you jump into water or by using a nose plug. Naegleria fowleri cannot infect you by drinking water that contains the ameba.

Symptoms

Symptoms typically begin one-to-seven days after the infection occurs. However, it can be as many as 15 days before symptoms develop.

Common symptoms include headache, fever, nausea, vomiting and a stiff neck. Later symptoms include confusion, lack of attention, loss of balance, seizures and hallucinations. Once the Naegleria fowleri ameba causes infection, the illness progresses rapidly, most often resulting in death in one-to-12 days.

Treatment and Outcomes

Infection is fatal in about 95 percent of cases.

Since there is no cure, health care providers can only treat the symptoms.

More Information

Additional information on Naegleria fowleri can be found on the CDC's website.