The strain of E. coli linked to Costco chicken salad that sickened 19 people in seven states is more likely to be life-threatening than a recent outbreak that closed some Chipotle restaurants in the Northwest.

Health officials urged people who bought chicken salad at any U.S. Costco store on or before Friday 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. Five people have been hospitalized and two have developed a type of kidney failure, the Centers for Disease Control and Prevention said.

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 fallen 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 illnesses are not related to a recent E. coli outbreak tied to Chipotle that sickened more than 40 people. Chipotle voluntarily closed 43 restaurants in Washington and Oregon and reopened them after deep cleaning and ordering new ingredients.

The strain linked to the Mexican food chain was identified as E. coli 026, while the one tied to Costco is E. coli 157, which the CDC said is more likely to be harmful, 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 Chipotle outbreak, said the problem appears serious because two people have developed kidney failure. People were hospitalized in the Chipotle outbreak, but no one developed kidney failure.

Marler said the new case shows 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.

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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.

The human intestines contain hundreds of E. coli and similar bacteria strains. Most are harmless, but a few can cause serious problems.

Health officials say the incubation period is three to seven days from the time of exposure.