(WHTM) — Swimmers in the Midstate should be on the lookout for E. coli.

The nonprofit Lower Susquehanna Riverkeeper Association, which independently tests the watershed weekly for bacteria, is advising people to avoid contact with water in several locations.

According to a June 12 test, samples from 16 sites in the Midstate recorded high levels of E.coli.

The organization recommends avoiding water at these locations:

York and Cumberland Counties

• New Cumberland Boat Launch
• Lower Allen Community Park
• North Sherman Street Bridge
• Walnut Street Boat Launch
• Klines Run Park
• Lock 2 Boat Launch

Lancaster County

• Columbia River Park
• Blue Rock Boat Launch
• Pequea Boat Launch
• F&M Marietta Avenue Floodplain Restoration
• Landis Mill Covered Bridge
• Perelman Park Canoe Access
• Rock Hill Access
• Paradise Community Park

Dauphin County

• Swatara Creek Water Trail
• Boathouse Park

Only one location in the four counties reported back a sample with low levels: City Island.

E. coli is a type of bacteria that lives in the intestines of people and animals. Individuals who swim in waters with elevated E. coli levels risk getting sick with illnesses such as meningitis, septicemia, urinary tract infections and intestinal infection, according to the United States Geological Survey.

Levels can especially rise after storms, according to the Environmental Protection Agency, when water runoff and combined sewer systems empty fecal matter from humans and animals.