The Wisconsin Department of Health Services, the Illinois Department of Health and the CDC are looking into eight cases in which humans contracted infections caused by the Seoul virus, which is a rare virus carried by wild and domestic rats.
Here are seven things to know about the virus and the investigation, from the CDC and state health departments.
1. Seoul virus is a type of hantavirus carried by Norway rats, both wild and domesticated. It does not make the rats sick, but can infect humans if they are exposed to blood, saliva or urine or are bit by an infected rat. It is not spread from person to person.
2. The Seoul virus is found worldwide and causes a mild to moderate infection in humans, according to the CDC. Symptoms include fever, headache, nausea, blurred vision and a rash. Treatment typically involves supportive care, including giving patients liquids directly into the vein, but the antiviral drug Ribavirin has been successful in reducing severity of the illness. Mortality is low, with about 1 to 2 percent of patients dying.
3. Six people in Illinois who had direct exposure to rats tested positive for the virus. They had contact with the rats in two different ratteries, which are facilities where rats are bred. Five of the six affected individuals showed no signs of illness.
4. A rattery in Wisconsin bought rats from one of the two Illinois ratteries, and two Wisconsin residents have now tested positive for the virus. One of the residents was hospitalized.
5. All affected individuals have recovered, and none of the affiliated ratteries are currently selling rats.
6. Because Seoul virus is not transmitted from person to person, "the general public is at extremely low risk," said Illinois Department of Public Health Director Nirav Shah, MD. "Out of an abundance of caution, we want to let the public know in the event they have recently purchased rats from an affected facility and become ill." The CDC and the state health departments are working on a trace-back investigation to find other people who may be infected.
7. To avoid a Seoul virus infection, the CDC emphasizes hand-washing, avoiding bites and scratches and providing routine veterinary care to animals.