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Primary Amebic Meningoencephalitis - Frequently Asked Questions

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What is Primary Amebic Meningoencephalitis (PAM)?

Primary Amebic Meningoencephalitis or PAM is an infection of the brain and the membranous tissues that surround and cover the spinal cord and brain. The causative agent is an ameba from the genus Naegleria and species fowleriNaegleria fowleriNaegleria fowleri is commonly found in warm freshwater and soil.. The initial infective event has been linked to activities in fresh-water (untreated) and during the hotter months of the year. In very rare situations, Naegleria fowleri has been known to cause infection in humans. This infection of the meninges and brain tissue, once it has occurred, progresses rapidly, causing massive destruction of the brain and meningeal tissues, resulting in coma and death within 10 days from onset of symptoms. This infection is almost always fatal.

How does infection with Naegleria fowleri occur?

Naegleria fowleri infects people by entering the body through the nose. Generally, this occurs when people swim or dive in warm freshwater, especially stagnant ponds or lakes in warm climate areas. The ameba travels up the nose to the brain and spinal cord where it destroys brain tissue. The ameba may also enter the nose when nasal irrigation or sinus flushes are performed using plain tap water rather than sterile, distilled, or lukewarm previously boiled water.

What are the symptoms of Naegleria fowleriinfections - PAM?

Infections with Naegleria fowleri cause the disease PAM, a brain infection that leads to the destruction of brain tissue. In its early stages, Naegleria fowleri infection may be similar to bacterial meningitis. Initial symptoms of PAM start 1 to 7 days after infection. Symptoms may include headache, fever, nausea, vomiting, and/or stiff neck. Later symptoms may include confusion, lack of attention to people and surroundings, a loss of balance, seizures, and/or hallucinations. After the start of symptoms, the disease progresses rapidly and usually causes death occurs within 10 days, usually on the 5th or 6th day.

Is there effective treatment for infection with Naegleria fowleri?

It is not clear. Several drugs are effective against Naegleria fowleri in the laboratory. However, their effectiveness is unclear since almost all infections have been fatal even when people were treated. “Please go to the CDC website for up-to-date information on available treatments and their effectiveness.”

Is there a routine and rapid test for Naegleria fowleri in the water?

No. It can take weeks to grow and identify the ameba. Newer genetic detections tests for ameba are still under development. Water testing suggests that the ameba are so common that recreational water users should assume that there is a low level of risk when entering all warm fresh water in southern tier states such as Texas.

How does the risk of Naegleria fowleri infection compare with other water-related risks?

Although infections are severe, the risk of Naegleria fowleri infections is very low. There have been 30 reported infections in the U.S. during the 10 years from 2000-2009, despite millions of recreational water exposures each year. By comparison, during the ten years from 1996 to 2005, there were over 36,000 drowning deaths in the U.S.

Does PAM occur in Texas?

Just like the U.S., the risk of Naegleria fowleri infections is very rare in Texas. Cases that occur in the U.S. typically happen in states with warm climate and abundance of recreational waters such as Texas. From 1983 to 2012 there were 28 deaths from Naegleria fowleri infections in Texas.

Compared to other conditions such as drowning and other types of meningitis, PAM is very rare. In Texas, from 2004 to 2008, there were 3 cases of PAM, 749 deaths from drowning, and 225 cases of bacterial meningitis.

How can I reduce the risk of infection with Naegleria fowleri?

It is likely that a low risk of Naegleria fowleri infection will always exist with recreational use of warm freshwater lakes, rivers and hot springs. The low number of infections makes it difficult to know why some people have been infected compared to the millions of other people using the same or similar waters across the U.S. The only way to prevent Naegleria fowleri infections is to refrain from water-related activities. If you do plan to take part in water-related activities, here are some measures that might reduce risk:

  • Understand routes of exposure and use common-sense prevention practices to limit exposure risk.
  • Avoid water-related activities in bodies of warm freshwater during periods of high water temperature and low water levels
  • Hold the nose shut or use nose clips when taking part in water-related activities in bodies of warm freshwater such as lakes, rivers, or hot springs.
  • Avoid digging in or stirring up the sediment while taking part in water-related activities in shallow, warm freshwater areas.
  • If you use a Neti Pot or syringe for nasal irrigation or sinus flushes be sure to use only sterile, distilled or lukewarm previously boiled water.

Portions of these FAQs were developed by Naegleria workgroup sponsored by the Council or State and Territorial Epidemiologists and CDC.

For further information on protecting yourself from recreational water illnesses, go to

Last updated May 22, 2018