Logo courtesy of Butte County Public Health

BUTTE COUNTY, CA (MPG) - Butte County Public Health announced that recent water and sediment samples collected from Big Chico Creek tested negative for E. coli O157, the strain linked to an outbreak of illnesses connected to recreational water exposure during summer 2025.

Public Health officials said samples collected May 4 from several locations along the creek were analyzed by the State Water Board’s laboratory. The testing was part of an ongoing investigation into last year’s outbreak.

Butte County Public Health said it will continue consulting with the State Water Board in the coming weeks to determine whether additional testing will take place.

Officials cautioned that conditions in natural waterways can change quickly because of weather, wildlife activity, water flow and erosion from past wildfires. They noted the recent results represent conditions only at the time of sampling and do not guarantee future water quality.

According to Public Health, the testing specifically targeted E. coli O157, a rare strain of bacteria that can cause severe illness. Officials said the county does not routinely test Big Chico Creek and only began testing as part of the investigation into the 2025 outbreak.

Separately, the City of Chico conducts seasonal water quality monitoring at Sycamore Pool during warmer months to measure common E. coli levels typically found in natural waterways. The city may issue swimming advisories if bacteria levels exceed public health thresholds. Current Sycamore Pool monitoring results are available through the City of Chico website.

Public Health officials reminded residents that swimming and recreating in natural waterways always carries some level of risk, particularly for young children, older adults and people with weakened immune systems. Exposure to bacteria and other germs can occur if water is swallowed or enters the body through cuts or abrasions.

Officials recommend that people avoid swallowing creek water, wash their hands before eating or drinking, rinse off with clean water after swimming and avoid entering the water with open wounds or after recent illness. Public Health also advised parents to closely monitor young children and use properly fitted swim diapers for children who are not potty trained.

Symptoms of E. coli infection can include diarrhea, stomach cramps and fever. Residents who believe they may have contracted a waterborne illness are encouraged to contact their healthcare provider and report the illness to Butte County Public Health at 530-552-3929.