ST. PAUL — The notorious poop-germ is on the prowl this summer, closing down beaches across the metro area.

A more polite name might be “fecal indicator,” which is how it is described by Trisha Robinson of the state Department of Health.

Dangerous levels of E. coli bacteria has resulted in the closure of beaches on McCarrons Lake in Roseville, Tanners Lake in Oakdale, Carver Lake in Woodbury, two locations on Bde Maka Ska, and three other west-metro lakes.

It is suspected — but not yet proven — to be the culprit in a Lake Minnetonka incident July 4 which sickened more than 120 people.

Officials aren’t sure if this is an unusually high number of E. coli outbreaks.

“It’s not uncommon to see more of this in the dog days of summer,” said Robinson, supervisor of the Department’s Waterborne Diseases Unit.

Robinson explained there are hundreds of kinds of E. coli bacteria, and only a handful of them make people sick.

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Some types are found in contaminated food, such as spinach or ground beef, which trigger national recalls.

The kind that is closing metro-area lakes comes from one source — poop. The source of the E. coli is almost always from the feces of humans and animals, said Robinson.

In a rainy summer, she said, the water can wash goose dung into lakes.

More commonly, people themselves spread it. It happens when a baby with a dirty diaper wades in the water, or when someone takes a potty break without leaving the lake.

“We are our own worst enemy,” said Robinson. “It’s usually due to other people.”

Warmer weather raises water temperatures, she said, which also helps the bacteria grow.

Usually the closures last a short time, as the germs disperse and die off. The Carver Lake closing in Woodbury lasted only three days.

But some of them can close beaches for most of a season. Lake McCarrons Beach in Roseville was closed from July 10 to Aug. 8.

Robinson said that people can minimize their risks in any lake by:

  • Not swallowing lake water.
  • Avoiding lakes shortly after a rainfall.
  • Washing hands after swimming, and before eating.