UPDATE:

Marin County health officials have increased to six an estimate of the number of Marin residents suspected to be sickened by an unidentified exposure to E. coli.

Marin County Public Health Officer Dr. Matt Willis said Friday afternoon five confirmed and one presumptive case of the food-borne E. coli O157 infection has been reported to Marin County health officials since Sept. 22. Four of the patients are children.

Of the four patients hospitalized, two have been discharged; two other patients were not hospitalized. All six patients are stable and recovering or fully recovered. The infected individuals are residents of Tiburon, San Anselmo, Inverness and San Rafael.

No single source of the infection has been identified

Five confirmed and one presumptive case of the food-borne E. coli O157 infection have been reported to Marin County health officials in since Sept. 22, and four of the patients are children.

Of four patients hospitalized, two have been discharged; two other patients were not hospitalized. All six patients are stable and recovering or fully recovered, said Marin County Public Health Officer Dr. Matt Willis.

The patients are residents of Tiburon, San Anselmo, Inverness and San Rafael.

Marin County Department of Health and Human Services (HHS) and Environmental Health Services are working with the California Department of Public Health to gather information from clinicians, patients and food vendors to determine whether the cases might share a common source or be linked to cases outside of Marin.

The ongoing investigation has not identified any single food source of the infections. Environmental Health inspections of establishments where food may have been purchased or consumed by cases has not revealed any contaminated products or evidence for ongoing risk to the public.

A regional public health laboratory is collaborating with a state lab to perform DNA fingerprinting on the bacteria, which will help determine if people were infected with the same strain. Willis said the fingerprinting is a new technique that will help narrow the focus in finding potential links between cases.

E. coli infection usually occurs by eating foods containing the bacteria, and the people most at risk for serious illness are children and older adults or others living with weakened immune systems. Marin averages about five cases of E coli O157 each year.