Health officials are investigating how a rare rat virus called the Seoul virus infected eight people in Wisconsin and Illinois.
The Wisconsin Department of Health Services says all eight people had direct contact with rats at Illinois and Wisconsin ratteries, which are rat-breeding facilities.
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Humans can become infected with the Seoul virus through direct contact with rats, though the virus cannot spread from person to person. Symptoms can include fever, chills, nausea, aches and pains or irritated skin. Not everyone experiences symptoms.
Both people in Wisconsin recovered from the infections. Five of the six people in Illinois showed no symptoms.
Wisconsin, Illinois and federal health officials are investigating the source of the virus. None of the ratteries involved are currently selling rats.