It seemed like a headache, nothing more. But when pain killers and a trip to the emergency room didn't fix Aaron Evans, the 14-year-old asked his dad if he was going to die.
"No, no," David Evans remembers saying. "We didn't know. And here I am: I come home and I'm burying him."
What was bothering Aaron was an amoeba, a microscopic organism called Naegleria fowleri that attacks the body through the nasal cavity, quickly eating its way to the brain. The doctors said he probably picked it up a week before while swimming in the balmy shallows of Lake Havasu.
Such attacks are extremely rare, though some health officials have put their communities on high alert, telling people to stay away from warm, standing water.
"This is definitely something we need to track," said Michael Beach, a specialist in recreational water-born 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, Naegleria infected 23 people from 1995 to 2004. This year health officials say they've noticed a spike in cases, with six Naegleria-related cases so far — all of them fatal.
Though infections tend to be found in southern states, Naegleria has been found almost everywhere in lakes, hot springs, even some swimming pools. Still, the CDC knows of only several hundred cases worldwide since its discovery in Australia in the 1960s.
The amoeba typically live in lake bottoms, grazing off algae and bacteria in the sediment. Beach said 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 amoeba destroys tissue as it makes its way up to the brain.
People who are infected tend to complain of a stiff neck, headaches and fevers, Beach said. 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, Beach said.
"Usually, from initial exposure it's fatal within two weeks," Beach said.
Researchers still have much to learn about Naegleria, Beach said. 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.
In addition to the Arizona case, health officials reported two cases in Texas and three more in central Florida this year. In response, central Florida authorities started an amoeba telephone hot line advising people to avoid warm, standing water, or any areas with obvious algae blooms.
Texas health officials also have issued news releases about the dangers of amoeba attacks and to be cautious around water. 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.
Lake Havasu City officials also are discussing how to deal with rare amoeba attacks in the wake of Aaron Evans' death. "Some folks think we should be putting up signs. Some people think we should close the lake," city spokesman Charlie Cassens said. City leaders haven't yet decided what to do.
Beach warned that people shouldn't panic about the dangers of brain-eating amoeba. Infections are extremely rare when compared with the number of times a year people come into contact with water. And there have been occasional years during the past two decades that experts noticed a similar spike in infections.
The easiest way to prevent infection, Beach said, 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, he said.
David Evans has tried to learn as much as possible about amoebas during the past month. But it still doesn't make much sense. The questions keep swirling around his head. Why now? His family has gone to Lake Havasu countless times without a problem. Have people always been in danger? Did city officials know about amoebas? Can they do anything to kill them off?
"It's been pretty heavy-duty," he said.
Evans lives within eyesight of Lake Havasu, a bulging strip of the Colorado River that separates Arizona from California. Temperatures hover in the triple digits all summer, and like almost everyone else, the Evans family looks to the lake to cool off.
On Sept. 8, he brought Aaron, his two other children and his parents to Lake Havasu to celebrate his birthday. They ate sandwiches and spent a few hours splashing around one of the beaches.
"For a week, everything was fine," he said.
Then Aaron got the headache that wouldn't go away. Evans took him to the hospital, and doctors thought his son was suffering from meningitis. Aaron was rushed to another hospital in Las Vegas.
Evans tried to reassure his son, but he had no idea what was wrong. On Sept. 17, Aaron stopped breathing as David held him in his arms.
"He was brain dead," David said. Only later did doctors realize the boy had been infected with Naegleria.
"My kids won't ever swim on Lake Havasu again."