Story highlights An eight-state outbreak of salmonella infections has been linked to pet guinea pigs

Pet rodents can carry Salmonella bacteria even when they look healthy and clean

(CNN) A multistate outbreak of salmonella has been linked to pet guinea pigs, according to the US Centers for Disease Control and Prevention. Nine people have been infected in eight states, and one person has been hospitalized, but no deaths have been reported.

A continuing investigation by the CDC, several states and the US Department of Agriculture Animal and Plant Health Inspection Service has found evidence that contact with pet guinea pigs is the likely source of the salmonella outbreak.

The illnesses started between July 17, 2015, and December 15.

Most people infected with salmonella experience symptoms such as diarrhea, fever and abdominal cramps 12 to 72 hours after being exposed to the bacteria. The illness lasts about four to seven days.

Most people recover without treatment, but in some cases, the diarrhea can be so severe that patients need to be hospitalized. In rare cases, salmonella can cause death unless a patient receives prompt treatment with antibiotics.

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