(CBS SF) — A multi-state outbreak of drug-resistant salmonella is being linked to contact with pig ear dog treats, authorities said Wednesday.

The U.S. Centers for Disease Control and Prevention, U.S. Food and Drug Administration, and public health officials are investigating the salmonella outbreak, which has infected a total of 45 people in 13 states, according to the CDC.

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CDC: Notice on Salmonella Outbreak Linked to Pig Ear Dog Treats

The states where the infections were reported are California, Illinois, Indiana, Iowa, Kansas, Massachusetts, Michigan, Missouri, New York, North Dakota, Pennsylvania, South Carolina, Wisconsin.

12 people have been hospitalized, the CDC said. No deaths have been reported.

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The illnesses began November 18, 2018 through June 13. Interviews with those affected indicated pig ear dog treats are the likely source of this outbreak, but a common supplier of the dog treats has not been identified.

Most people with salmonella develop diarrhea, fever, and stomach cramps 12 to 72 hours after being exposed to the bacteria. The infection usually lasts four-to-seven days and most recover without treatment; however some people may need to be hospitalized and young children, pregnant women, the elderly and people with weakened immune systems are more likely to have a severe illness.

The CDC said the investigation is still ongoing.

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