(CNN) -- Ray Herrera does not mince words about what his 12-year-old son, Jack, went through.

Jack Herrera is one of six people to die this year because of the naegleria fowleri amoeba.

"It's beyond description to watch your most precious, beautiful, wonderful, loved one become a vegetable essentially and then die," Herrera said.

In August, Jack returned from summer camp that included swims in Texas' Lake LBJ. Five days after coming home he was dead, killed by a microscopic amoeba.

"He was the happiest boy anyone ever knew," Herrera said.

Jack is one of six people to die this summer in the United States from the naegleria fowleri amoeba.

All were believed by health officials to have contracted an infection from the amoeba from swimming in warm, freshwater lakes, rivers or natural springs. See timeline of the sudden deaths »

There is no risk from properly chlorinated swimming pools, according to the Centers for Disease Control and Prevention.

The amoeba enters the human body through the nose. It then travels to the brain, where it begins to feed.

Symptoms of the amoeba's rampage begin 1 to 14 days after infection and resemble the flu. At the onset of those symptoms the amoeba victim's health swiftly declines. Watch how to reduce risk of contracting the amoeba »

At this point, says Dr. Kevin Sherin of the Orange County Health Department who is investigating three deaths this summer in Florida, "It's progressing very rapidly and then there's a downhill course for them there. Folks lapse into a coma, there are abnormal movements of the eyes and a terrible cascade of events leading to the actual death of parts of the brain."

Although exposure to the amoeba is usually fatal, Sherin says a cocktail of drugs can fight the amoeba if administered in time. The key, he says, is identifying the amoeba early.

In the hot summer months when the amoeba flourishes, he said, doctors need to learn to look for the symptoms of an amoeba-related illness.

"Physicians have to consider it. The public needs to consider it," Sherin said. "If you have a flu-like illness or a bad headache following swimming in a freshwater body and the temperature is over 80 degrees Fahrenheit, be aware of this."

However, only a handful of doctors have seen a patient with the rare amoeba.

Until this summer there were only 24 known cases of it in the U.S. since 1989, according to the CDC.

Health officials cannot explain the spike in cases this summer, except that weather plays a factor.

"Because it's been such a hot summer, that has contributed to warmer water temperatures and lower water levels and that makes an ideal environment for the amoeba," said Dr. Rebecca Sunenshine of the Arizona Department of Health, which is investigating a death last month there tied to the amoeba.

Another question health officials have is why the amoeba seems to appear more often in young males. All six victims this summer were male, ages 10 to 22 years old. One theory, the CDC says, is that young males might be more likely to engage in water sports such as water skiing or wakeboarding. Those can lead to greater exposure to the amoeba.

But other than wearing nose plugs while swimming or staying out of freshwater above 80 degrees Fahrenheit, there is little people can do to prevent exposure to the amoeba.

Health officials say federal or local governments have few tools to combat the amoeba.

Even testing the water for amoeba levels, said the CDC's Dr. Michael Beach, would be of minimal benefit to swimmers.

"It would be very difficult because the testing procedures wouldn't tell you what's going on until days after people would actually be in that water." Beach said this week on CNN's American Morning.

"So, you have to assume that it's there and try and reduce these risks even further. This is an extremely rare infection, so we have to keep that in perspective as well, although it's very severe," Beach said.

In Orange County, Florida, county health department officials have rejected calls to close the lakes this summer. Dr. Kevin Sherin said the department does not have the authority to deny access to public lakes and that privately owned lake areas would remain open regardless of any action to close the lakes.

Instead, the health department has posted signs at 15 swimming and boating areas where people may face exposure to the amoeba.

The effectiveness of the signs appears mixed. When a CNN crew recently visited a bathing area near a natural spring, the water was packed with families.

As he sunbathed near a sign warning of amoebas, John Walters seemed unconcerned about danger possibly lurking beneath the clear, inviting waters. "It's no worse I suppose than the gator signs over there and somebody did get attacked here once." E-mail to a friend

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