A killer amoeba living in lakes enters the body through the nose and attacks the brain where it feeds until you die, US experts say.

The microscopic bug killed six boys and young men in the US this year. The spike in cases has worried health officials, and they are predicting more cases in the future.

"This is definitely something we need to track," said Michael Beach, a specialist in recreational waterborne illnesses for the Centers for Disease Control and Prevention.

"This is a heat-loving amoeba. As water temperatures go up, it does better," Beach said. "In future decades, as temperatures rise, we'd expect to see more cases."

According to the CDC, the amoeba called Naegleria fowleri killed 23 people in the United States, from 1995 to 2004. This year health officials noticed a spike with six cases - three in Florida, two in Texas and one in Arizona.

In Arizona, David Evans said nobody knew his son, Aaron, was infected with the amoeba until after the 14-year-old died on September 17. At first, the teen seemed to be suffering from nothing more than a headache.

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