Health officials in Butte County are investigating a cluster of illnesses linked to E. coli O157, a specific variant of the bacterium, that occurred in Big Chico Creek during the summer of 2025.
The Butte County Public Health (BCPH) department collected water and sediment samples on May 4 from multiple locations across the creek to identify the source of the outbreak. These samples were sent to the State Water Board laboratory for analysis.
However, laboratory results did not detect the O157 variant in any of the samples, leaving the exact origin of the illnesses unclear. The investigation continues as authorities work to ensure the safety of the creek and prevent further cases.