Fresno County health investigators said 15 E. coli cases from a recent outbreak had been confirmed as of Friday afternoon, reports the Fresno Bee.

One man has been hospitalized with hemolytic uremic syndrome, a kidney complication from the bacterial infection, said David Luchini, communicable disease division manager for the Fresno County Department of Community Health.

Most of the cases appear to be related to three private gatherings — two graduation parties and a wedding. But health workers are still investigating illnesses that might be related to other events.