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Balamuthia mandrillaris ameba infection

Balamuthia mandrillaris is a free-living ameba (a single-celled organism) found in soil and dust. Exposure to Balamuthia is likely to be common because of how widespread it is in the environment. However, very few cases of disease in humans have been found worldwide since Balamuthia was discovered.

What is Balamuthia mandrillaris?

Balamuthia is a free-living ameba found in the environment. It was first identified in 1986 in a specimen from the brain of a baboon that died in the San Diego Wild Animal Park. Since then, approximately 200 cases of Balamuthia disease have been reported worldwide; approximately 70 of those cases have been reported in the United States. Little is known at this time about how a person becomes infected.

Balamuthia can cause Balamuthia granulomatous amebic encephalitis (GAE), a serious brain infection that is usually fatal. Balamuthia GAE occurs when the Balamuthia amebae infect the body, possibly through skin wounds and cuts, or when dust containing Balamuthia is breathed in through the nose or mouth. The amebae may travel to the brain directly through the sinuses, or through the blood stream. Balamuthia GAE is a very rare but usually fatal disease.

Why is CDC concerned about Balamuthia infection now?

During 2009-2010, CDC identified two clusters of transplant-transmitted Balamuthia GAE. In each cluster, there were four transplant recipients; two transplant recipients became ill while two other recipients from each donor have not shown symptoms. The second cluster of cases is still being investigated. Both clusters are described in the September 17, 2010 issue of the MMWR.

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