Amoeba: Naegleria fowleri Brain Infection Rare but Fatal

Medical Author: Melissa Conrad Stöppler, MD
Medical Editor: William C. Shiel Jr., MD, FACP, FACR

The death of six people in summer 2007 as a result of infection with the Naegleria fowleri amoeba raised widespread awareness of this rare infection. Naegleria fowleri is an amoeba found worldwide in warm bodies of water, but human infection is extremely rare. Until the six cases in summer 2007, the U.S. Centers for Disease Control and Prevention (CDC) reported only 23 cases of the condition between 1995 and 2004.

All of those who died in 2007 were believed to have contracted the infection from swimming in freshwater lakes, rivers, or springs during the hot summer months. Health Department officials in the affected areas pointed out that hot air temperatures raised water temperatures to levels (above 80 degrees Fahrenheit) in which the amoeba thrives. The victims in summer 2007 were all young males between the ages of 10 and 22. Those who swim in warm freshwater sources, particularly those who participate in water sports and play in a manner in which entry of water into the nose is likely, are at risk for the infection.

The Naegleria fowleri amoeba enters the nose and then migrates to the brain to cause a disease known as primary amebic meningoencephalitis (PAM). Symptoms, typically those of a flu-like illness, begin within two weeks of exposure. The symptoms worsen quickly until coma and brain death ensue. Certain drugs have been shown to be effective against Naegleria fowleri in the laboratory, but it is not known if these same medications will be effective in treating the condition in humans. Most reported infections of humans have been fatal.