It may seem like taken from the X-files, but the bug is real. Its last victim is a 14-year-old boy who waded in the Lake Havasu between Arizona and California in September 2007. This is the sixth victim in 2007 of a type of Amoeba that makes its way to the brain through the nasal cavity, and destroys it.

Naegleria fowleri, first discovered in Australia in the 1960s, killed 23 people from 1995 to 2004, and even if the cases are rare, they are 100 % lethal. "This is definitely something we need to track. This is a heat-loving amoeba (preferred temperatures: 25-35o C (77-95 o F)). As water temperatures go up, it does better. In future decades, as temperatures rise, we'd expect to see more cases.", said Michael Beach, a specialist in recreational water-born illnesses for the CDC.

Naegleria has been found almost all around US in lakes, hot springs, even swimming pools, but infections come mainly from southern states (the other cases of 2007 come from Texas (2) and Florida (3)). The amoeba typically inhabits lake bottoms, feeding on algae and bacteria in the sediment. "People become infected when they wade through shallow water and stir up the bottom. If someone allows water to shoot up the nose -- say, by doing a cannonball off a cliff -- the amoeba can latch onto the person's olfactory nerve."

The bug destroys tissue on its way towards the brain. It causes olfactory impairment (taste and smell), vomiting, nausea, fever, headache, and the rapid onset of coma and death in two weeks.

The amoeba first penetrates the olfactory mucosa and nasal tissues, causing severe necrosis and hemorrhage in the olfactory bulbs. "People who are infected tend to complain of a stiff neck, headaches and fevers. In the later stages, they'll show signs of brain damage such as hallucinations and behavioral changes. Once infected, most people have little chance of survival. Some drugs have been effective stopping the amoeba in lab experiments, but people who have been attacked rarely survive. Usually, from initial exposure it's fatal within two weeks", Beach said.

"Researchers still have much to learn about Naegleria. For example, it seems that children are more likely to get infected, and boys are infected more often than girls. Experts don't know why. Boys tend to have more boisterous activities (in water), but we're not clear," he said. "People seem to think that everything can be made safe, including any river, any creek, but that's just not the case," said Doug McBride, a spokesman for the Texas Department of State Health Services.

Still, experts say people shouldn't panic, since infections are extremely rare compared to how much people enter in contact with the water. "The easiest way to prevent infection is to simply plug your nose when swimming or diving in fresh water. You'd have to have water going way up in your nose to begin with to be infected", said Beach.