The Balamuthia amoeba was first found in 1990 in a mandrill baboon. Unlike many amoebas, this one is unusual because it is not a parasite and does not need a host to live on, Wiser said. It feeds off bacteria. The organism is believed to live in freshwater ponds, and doctors think most victims come into contact with it while swimming, according to research presented at an infectious diseases conference in Buenos Aires last year. It enters humans through their eyes or lesions, Wiser said.
Doctors think the amoeba kills only people who have some other problem with their immune systems.
Fever and other flulike symptoms are followed by slurred speech and loss of consciousness in humans affected by the amoeba, Wiser said. Chronicle staff writer Mark Martin contributed to this report.