Seoul virus: a member of the Hantavirus family of rodent-borne viruses. The virus is carried by wild Norway rats and can be found worldwide. People usually become infected when they come in contact with infectious body fluids (blood, saliva, or urine) from infected rats or are bitten by an infected rat. Most cases in humans have been reported in Asia. Person-to-person spread of the virus does not occur. Infected rats typically do not appear ill. Not all people infected with the Seoul virus will get symptoms. The infection usually is milder than those seen with other Hantaviruses. Symptoms may include fever and chills, severe headache, back and abdominal pain, blurred vision, redness of the eyes, or a skin rash. Rarely, infection also can lead to kidney disease. Most people infected with Seoul virus will recover fully. In early 2017, an outbreak of the illness was reported in Illinois, Indiana, and Wisconsin after reports of illness in December 2016 in 2 people who maintained a home-based rat-breeding facility in Wisconsin. Those affected had purchased rats from animal suppliers in Wisconsin and Illinois.