Evanston's beaches are closed for swimming Wednesday due to high counts of the bacteria E. coli.
The city issued an advisory Wednesday morning, notifying residents that E. coli counts were higher than recommended.
City staff test the water from Evanston's five beaches and the dog beach daily for E. coli levels. The samples take approximately 18 hours to process, and the most recent sample was recorded just above the accepted level.
Water must be resampled before the beaches can open again. According to the city, it will be at least 24 hours before staff can determine what current E. coli levels.
Natural die-off, wind, waves and ultraviolet light from the sun all contribute to reduction of E. coli levels. The bacteria lives in the digestive systems of humans and other warm-blooded animals, and can cause diarrhea, nausea, vomiting, abdominal pain, headache and low grade fever, according to the city.
E. coli makes its way into the lake via several routes, including illegal sewer connections to storm sewers or roadside ditches, storm runoff following a heavy rain, wild and domestic animal waste products, agricultural runoff and swimmer defecation, according to the city.