What is primary amebic meningoencephalitis?
Primary amebic meningoencephalitis (PAM) is a rare but nearly always fatal disease caused by infection with an ameba (single-celled living organism) called Naegleria fowleri.
How does infection with Naegleria fowleri occur?
Naegleria fowleri enters the body through the nose and travels to the brain, where it destroys brain tissue and causes swelling and death. Naegleria fowleri typically enters the nose when people go swimming or diving in bodies of warm freshwater, such as ponds, lakes and rivers. Very rarely, people can become infected by submerging their heads during religious practices or irrigating their sinuses (nose) using contaminated tap water.
No one has reported a Naegleria fowleri infection due to drinking contaminated water, or swimming in a properly cleaned, disinfected and maintained pool.
Where is Naegleria fowleri found?
Naegleria fowleri has been identified in freshwater specimens worldwide. Naegleria fowleri is not found in salt water. In the United States, the majority of Naegleria fowleri infections have occurred after swimming in freshwater located in southern states. In 2012, infection with Naegleria fowleri occurred in a child after swimming in a Minnesota lake. The Illinois Department of Public Health has not received any reports of Naegleria fowleri infection.
Naegleria fowleri can be found in:
- Bodies of warm freshwater, such as lakes and rivers
- Geothermal water, such as hot springs
- Geothermal drinking water sources
- Warm water discharge from industrial plants
- Swimming pools that are not properly maintained
- Water heaters
How common is Naegleria fowleri in the environment?
Previous water testing has shown that Naegleria fowleri is commonly found in warm freshwater venues. Therefore, recreational water users should assume a low level of risk when entering all warm freshwater.
Who gets primary amebic meningoencephalitis?
People with PAM usually have a recent history of recreational activity in lakes, ponds or inadequately chlorinated swimming pools. In most situations, the affected individuals have been previously healthy children or young adults.
How common is primary amebic meningoencephalitis?
PAM is an extremely rare disease. From 2002 to 2011, 32 infections were reported in the United States. Infections are more likely to occur during the summer months (July, August, and September) when water temperatures are high and water levels may be low.
What are the symptoms of primary amebic meningoencephalitis?
The initial symptoms of PAM may include headache, fever, nausea, vomiting and stiff neck. Later, infection may result in confusion, loss of balance, seizures, hallucinations and coma.
How soon do symptoms appear?
Initial symptoms of PAM typically begin one to seven days after infection. After the start of symptoms, the disease progresses rapidly and death usually occurs within 5 days (range 1 to 12 days).
Can PAM be spread from person to person?
No, PAM cannot be spread from person to person.
What is the treatment for primary amebic meningoencephalitis?
It is unclear whether PAM can be successfully treated. Several drugs have been effective against Naegleria fowleri in the laboratory. However, almost all reported cases of PAM have been fatal in humans, even when treated with similar drug combinations.
How can primary amebic meningoencephalitis be prevented?
The only certain way of preventing PAM is to avoid water-related activities in warm, untreated or poorly treated water. It is likely that a low risk of contracting PAM will exist with recreational use of warm freshwater ponds, lakes, rivers, and hot springs.
How is primary amebic meningoencephalitis diagnosed?
PAM can be difficult to diagnose. The disease progresses quickly, but it can take weeks to identify the ameba in the laboratory. Current diagnostic tools include evaluating cerebrospinal fluid, brain imaging, and culture in the laboratory. New detection tests are under development.
When taking part in water-related activities, you can take actions to reduce the risk of water going up the nose and lowering the chances that Naegleria fowleri may be in the water. These actions could include:
- Hold your nose shut, use nose clips, or keep your head above water when taking part in water-related activities in bodies of warm freshwater.
- Avoid water-related activities in warm freshwater during periods of high water temperature and low water levels.
- Avoid digging or stirring up sediment while taking part in water-related activities in shallow, warm freshwater areas.
Adapted from the U.S. Centers for Disease Control and Prevention website.