Editor's note: The 14-year-old boy described in this story, Hunter Boutain, has died, his family reported Thursday afternoon.

State and national health officials are trying to determine whether Minnesota is becoming a more hospitable place for a deadly water amoeba that has posed a greater risk to swimmers in southern states.

The Centers for Disease Control and Prevention and the Minnesota Department of Health are reviewing lab tests on a child who contracted a life-threatening brain infection that officials suspect is linked to the parasite.

Fourteen-year-old Hunter Boutain is in critical condition after being infected while swimming in Lake Minnewaska in Pope County.

If his case is confirmed, it would be Minnesota's third case of the Naegleria fowleri amoeba since 2010. Two other victims, both children, died from their infections.

State health officials were stunned when the amoeba claimed its first Minnesota victim that year. The parasite, which causes primary amebic meningoencephalitis, had never been found this far north.

That August, the weather had been very warm and health officials suspected those conditions helped the amoeba thrive in one of the small, shallow lakes where the first victim, a 7-year-old girl, had gone swimming.

Two years later, a 9-year-old boy was infected in the same lake. Afterward, health officials in Washington County closed the beach to swimmers.

This week's case puzzled state health officials because it occurred in a much bigger lake that has not been subject to a recent heat wave.

"It is not what we think of as typical because the risk is greater when water temperatures are higher and water levels are lower," said Trisha Robinson, waterborne diseases unit supervisor for the Minnesota Department of Health. "And we haven't experienced that big heat wave yet in Minnesota."

A warming climate could be making it easier for the amoeba to thrive in Minnesota waterways. But Robinson said there isn't enough evidence to support that theory yet. She said it's just as likely that this new case was an unfortunate coincidence, coming so soon on the heels of the state's other cases.

"Naegleria can be found in fresh water all over the world," she said. "It can be found in lower temperatures and your risk would increase as water temperatures go up. But there is a risk even when [temperatures are] lower."

That risk is still extremely low, Robinson said.

Officials at the CDC say at least 133 people have been infected by the amoeba in the United States over the last five decades. Most infections have been traced to contaminated recreational water.

However, a few people have been infected after rinsing their noses with tap water, and at least one child was sickened after using a backyard Slip 'N Slide, CDC officials say.

Agency officials say people cannot contract the infection from drinking water contaminated with Naegleria.

Dr. Stacene Maroushek, a pediatric infectious disease physician at Hennepin County Medical Center, said the amoeba enters the brain through the nasal cavity. She said activities like diving or jumping into the water seem to pose the greatest risk.

"Try to avoid getting water up the nose," she said. "Use nose plugs or at least try not to do diving that pushes water up the nose and things. And that would hopefully minimize the risk."

One Minnesota group that has worked to educate swimmers about the importance of using nose plugs is Swim Above Water, chaired by Heidi LaMeyer. She and her husband formed the group a few years after the death of their 11-year-old daughter Hailee, who contracted an unexplained brain infection in 2008 after swimming in a small lake about a block from her Forest Lake home.

The Naegleria fowleri amoeba was never confirmed as a cause of death because there was no autopsy.

LaMeyer said two years later, when Minnesota confirmed its first case, state health officials told her it seemed likely that the amoeba had caused her daughter's death. Health Department officials say they don't dispute her account.

This spring, Swim Above Water took a break from its activities because people didn't seem as interested in the message.

"Because we haven't had a death in Minnesota in a couple of years, it sort of felt like we needed to rest it just a little bit," LaMeyer said. "People weren't really wanting to hear it, because it was becoming, 'oh, that's something that happens in the south. We don't need to worry about that in Minnesota.'"

LaMeyer said Swim Above Water now plans to revive its education messages. It also will try to raise more research funds to study the amoeba and find better ways to treat the deadly brain infections it causes.