Michael John Riley Jr. was innocently swimming with his cross-country team at Sam Houston Park in Houston on August 13 when unknowingly came in contact with the Naegleria fowleri amoeba.  Over the next few days, the teen began to have a severe headache and within days, had lost all brain function.

The 14-year-old star athlete died Sunday, just days before the beginning of his freshman year of high school.  He had qualified for the Junior Olympics three times in track.

According to cnn.com, Naegleria fowleri is a one-celled organism that is usually found in warm fresh water, like lakes and rivers.  Contact with the amoeba can result in a brain infection, known as primary amebic meningoencephalitis, or PAM.

Infections due to contact with the amoeba are rare, but usually fatal.  The disease is not contagious, and can not be caught from drinking water.  Usually the amoeba enters the body through the nose when swimming or diving, and travels up to the brain.

Only about 133 cases have been documented in the past 53 years, according to the Center for Disease Control, with only three survivors recorded.  Most illness are from warm-weather states across the South and Southwest.  It is possible to get the disease from pools that are inadequately chlorinated, but that is an extremely rare occurrence.

Prevention of the disease is very difficult.  Because of the rarity of the infections, it is hard to predict where the next case may appear.  It is also unknown why certain people become infected, while others swimming in the same area do not.   Every year millions of people swim recreationally in lakes and rivers and do not become infected.

Experts advise avoiding swimming in stagnant water or water that has an unpleasant odor.  They also advise not stirring the bottom sediment in shallow fresh water areas, and recommend using nose plugs when swimming in lakes and rivers.