SEATTLE - The Centers for Disease Control and Prevention says the number of people affected by an E. coli outbreak linked to Costco chicken salad will likely grow over the next few weeks, even though the product has been removed from store shelves.

The agency said Wednesday the spread of foodborne illness takes time to track, especially when it's happening in multiple states.

Dr. Robert Tauxe of the CDC commended state health officials for quickly discovering the outbreak and helping find the links across seven states.

Tauxe says the CDC has already identified a DNA fingerprint of the E. coli strain that connects all 19 ill people.

Five of those people have been hospitalized, including two with kidney failure. Tauxe says they have all been told they are getting better.

Six people have fallen ill in Montana, five in Utah, four in Colorado, and one each in California, Missouri, Virginia and Washington state.

Costco has not returned calls seeking comment.