Officials studying what sickened July 4th boaters on Lake Minnetonka, as beaches elsewhere close

Public beaches in Excelsior and across the Twin Cities are closed due to bacteria, as authorities work to find what sickened boaters who were at Lake Minnetonka's Big Island over the July 4th weekend.

Beaches in Minneapolis and Chaska were shut down after local officials found E. coli in the water in several lakes. So far, no illnesses have been reported by people using those beaches.

E. coli was also blamed for the Excelsior closure, which was not being linked to the illnesses at Big Island.

Last week, Minneapolis officials closed the 32nd Street and Thomas beaches at Bde Maka Ska, formerly known as Lake Calhoun, and the Lake Hiawatha Beach through at least Wednesday, or until E. coli levels stabilize. The Minneapolis Park and Recreation Board closed the beaches after large volumes of stormwater flowed into the lakes, causing bacteria levels to exceed state guidelines. Park officials will reopen the three beaches when bacteria levels drop.

Chaska city officials announced Tuesday they were closing the Clayhole Swim Beach at Fireman's Park after finding E. coli in recent water tests. The beach will remain closed until further notice as a precautionary measure, city officials said in a statement, and water testing will continue during the closure. Lifeguards will remain on duty from noon to 7 p.m. during the closure. Updates will be provided on the Chaska Community Center website.

E. coli, or Escherichia coli, is a species of bacteria that normally lives in the intestines of healthy people and animals, according to the Minnesota Department of Health's website. More than 700 types of E. coli have been identified, most of which are harmless or cause brief diarrhea. A few strains can cause more severe abdominal cramps, bloody diarrhea and vomiting.

Rain can increase bacteria content in lakes by washing lawn fertilizer and animal feces into the water, said Joe Jurusik, supervising environmentalist for Hennepin County. Boat owners sometimes illegally dump human waste into the water, too, he said.

But the illnesses on Big Island probably weren't directly connected to the water problems at Excelsior beaches, Jurusik said. "Do you know how many billions of gallons are in Lake Minnetonka? The solution is dilution, so it would be pretty unlikely that the beach got infected from Big Island."

Dave Johnson, Hennepin County's epidemiology manager, said Tuesday that his department had received more than 30 reports from people experiencing vomiting, diarrhea or cramps after attending the typically crowded holiday celebrations on boats surrounding Big Island.

"The symptoms we're dealing with are really consistent with [illness caused by] food and or water exposure," Johnson said. "This many people being sick at once is not very common. ... We are considering this an outbreak and are investigating it as an outbreak."

County officials have asked people reporting illness to submit stool samples, which will be analyzed by the Department of Health. Results are expected in a couple of days, Johnson said.

He urged people experiencing vomiting or diarrhea to avoid swimming or preparing food, and to wash their hands frequently. It's not known if the illness came from food or the water.

Carolyn Marinan, a county spokeswoman, said the mother of a sick child alerted the county Monday and provided contact information for others who became ill. Epidemiologists are testing those individuals and will send the results to the Department of Health for analysis.

Staff writer Dan Browning contributed to this report.