People who bought chicken salad at any U.S. Costco store on or before Friday were advised to throw it away, even if no one has gotten sick.
The strain of Shiga toxin-producing E. coli can be life-threatening, but no deaths have been reported in the current outbreak. The Centers for Disease Control and Prevention said five people have been hospitalized and two have developed a type of kidney failure.
The CDC and state health officials were investigating and have not yet determined what ingredient in the rotisserie chicken salad made and sold in Costco Wholesale stores could be the source of the outbreak.
Six people have become ill in Montana, five in Utah, four in Colorado and one each in California, Missouri, Virginia and Washington state. The CDC said the illness reports began on Oct. 6 and involved people from age 5 to 84.
The outbreak is not related to a recent case involving Chipotle restaurants in which more than 40 people were sickened. That strain was identified as E. coli 026.
The current strain has been identified as E. coli 157, which the CDC said is more likely to be life-threatening, especially in young children.
A call to Costco headquarters in Washington state seeking comment was not immediately returned.
Seattle attorney Bill Marler, who is representing people sickened in the previous Chipotle outbreak, said the current problem appears serious since two people have developed kidney failure. People were hospitalized in the Chipotle outbreak, but no one developed kidney failure.
Marler said the new case is a good example of why food safety is so crucial.
"Costco has always been a leader in food safety at retail, it just goes to show you how important controlling your supply chain is," Marler said.
The human intestines contain hundreds of E. coli and similar bacteria strains. Most are harmless, but a few can cause serious problems.
Symptoms of E. coli infection include diarrhea, abdominal cramps, nausea and vomiting.
The bacteria are associated with animal waste but aren't just associated with meat. E. coli can be spread in indirect ways on produce.
Health officials say the incubation period is three to seven days from the time of exposure.