The father of a boy who died from a rare amoeba after swimming in Stillwater's Lily Lake is free to resume his lawsuit against the city for failing to warn of its dangers, the Minnesota Court of Appeals said Monday.

"I don't want to see this happen to any more kids. Two kids in one lake just isn't right," Jim Ariola said of his suit, filed nearly two years ago. "My son's not going to go down as a ­number, or a fluke. Without pushing and getting the awareness out there, nothing's going to be done."

Jack Ariola, 9, died in August 2012 from an amoeba traced to warm water in the lake, which has a small public beach. His death came two years after Annie Bahneman, 7, of Stillwater died from the amoeba after swimming in the same lake.

In Monday's decision, which partly reverses an earlier lower court ruling, the appeals court determined that Jim Ariola "has stated viable claims against the city."

At the same time, the appeals court affirmed the lower court's decision that two other government agencies — Washington County and the Minnesota Department of Health — can't be sued for the boy's death.

Ariola said he was disappointed that the appeals court hadn't reopened the county and state to the suit, but he said he appreciated its decision to restore the city portion.

"They all had a part in it," he said.

In court papers, Ariola alleges that the city altered the lake bottom to ­create a shallow area, resulting in especially warm water uniquely favorable to the Naegleria fowleri amoeba.

The microscopic flesh-eating amoeba, invisible to the human eye, becomes dangerous to humans when it enters the nose and travels to the brain, where it kills tissue and causes inflammation and death.

The city had argued that it couldn't prevent an amoeba that's naturally occurring in the environment. However, the appeals courts said, Stillwater failed to post signs at the city beach after Annie's death, warning of the potential ­presence of the amoeba.

"Appellant alleges that Jack's death was caused by the artificial condition of the improvements at Lily Lake, which were created and maintained by the city, and that the city knew that the improvements at Lily Lake were likely to cause death or serious bodily harm," Monday's opinion said.

"These allegations are sufficient to put the city on notice of the appellant's claims against it and state a valued claim for relief."

The city has 30 days to decide whether to appeal Monday's decision to the Minnesota Supreme Court. The city's attorney, Pierre Regnier, couldn't be reached for comment.

Ariola's attorney, Roger Strassburg, said Monday that he intended to pursue a suit against Stillwater depending on the outcome of a possible city appeal. The larger significance of the case, he said, is whether government takes responsibility for human welfare, "or are they entitled to just remain silent" and deny the public's right to protection.

"We look forward to holding the city fully responsible at trial," he said.

Washington County District Judge Susan R. Miles wrote in her December 2013 order that while she was sympathetic about Jack's death, she was powerless to create a ­remedy when none existed in law. She dismissed the suit against all three agencies.

"Where, as here, the loss is caused by a natural condition found in the environment, ­neither the law nor public ­policy should place a burden on taxpayers to absorb the economic burden of harm," Miles wrote.

However, the appeals court rejected the lower court's determination that a "recreational-use immunity" in state law necessarily protected ­Stillwater from a suit. Instead, the appeals court wrote, Jim Ariola could argue that the city "had failed to exercise reasonable care" to warn of altered conditions at the lake.

Public entities can be held liable if they "violated the standard of care that a private landowner owes a trespasser," the court wrote.

At a public meeting in Stillwater after Jack's death, a state health official said that many Minnesota lakes could have the parasite — particularly in prolonged stretches of summer heat — and that it can come and go unpredictably.

"It's not something that's quickly detectable, and it's not something that's going to be consistent," said Jim Koppel, deputy health commissioner.

Kevin Giles • 651-925-5037