A 7-year-old Stillwater girl who died from a rare form of meningitis 11 days ago had been swimming in the St. Croix River and two Washington County lakes in the weeks before her death, a Minnesota Department of Health epidemiologist said Tuesday.

Dr. Richard Danila said it's impossible to know which body of water supplied the specific organism that killed Annie Elizabeth Bahneman or why she became a victim of an extraordinarily rare disease never before documented in a Northern state.

"Since she was a very active little girl, very active family, it's hard to pinpoint one place," he said.

In addition to the St. Croix River, Annie and her family swam at a public beach at Lily Lake in Stillwater and a public swimming area at Little Carnelian Lake in Stillwater Township, Danila said.

The Health Department was reluctant to reveal where Annie swam because of concern that people would think they would be safer avoiding them. But the organism is found everywhere worldwide, Danila said.

"The risk is so low, but yet when it's your child [that died] the risk is 100 percent," he said.

Annie died at Children's Hospital in St. Paul four days after she fell sick with vomiting and a headache. Her death was caused by primary amebic meningoencephalitis (PAM), a rare form of meningitis, the health department said. The organism is known as Naegleria fowleri, an amoeba commonly found in warm fresh water and soil that causes a rare but severe brain infection that is nearly always fatal.

The organism enters the body through the nose during swimming or diving. It's most often present on hot days when temperatures in lakes and streams are 80 degrees or higher, the Health Department said.

Danila said it's not known why Annie fell sick when many other people who swam where she did, including her brothers, didn't experience any symptoms.

Annie had no health problems that might have contributed to her death, Danila said.

Her death is the first in Minnesota from the meningitis and probably in any other Northern state, said Doug Schulz, a department spokesman.

Schultz said it's the consensus at the department that the chance of anyone else becoming infected from the disease is "infinitesimal" because so few similar cases have occurred. In warmer Southern states, 121 deaths were recorded between 1937 and 2007, "contrasted with millions of swimmers," he said.

"If you're swimming in a body of water that's 80 degrees or higher, and it's mucky or murky, you might want to think twice," Schultz said, although he also pointed out that the "minuscule" risk declines even more as summer ends.

Danila said that public swimming pools aren't at risk because of chlorine treatments.

Annie's funeral was held Friday. Pink and purple balloons were tied to trees and fences for blocks around her Stillwater house. She would have been a first-grader at St. Croix Preparatory School.

Kevin Giles • 651-735-3342