Officials with the Centers for Disease Control and Prevention (CDC), The Illinois Department of Public Health (IDPH) and The Wisconsin Department of Health Services (DHS) are investigating eight cases of illnesses caused by the Seoul virus, which a very rare type of hantavirus carried by Norway rats.

Image/National Park Service
Image/National Park Service

Six cases of Seoul virus has been reported in individuals who had direct exposure to rats in two different Illinois ratteries. Ratteries are facilities where rats are bred. A rattery in Wisconsin purchased rats from the two Illinois ratteries and two Wisconsin residents have also tested positive for Seoul virus. Results of laboratory testing of rats at these facilities are pending.

“Because rats from ratteries are sold to and swapped among individuals, we are working with local health departments and the Centers for Disease and Prevention (CDC) to determine if there are additional cases,” said Karen McKeown, State Health Officer. “We are responding aggressively to protect and promote the health and safety of the people of Wisconsin.”

“Seoul virus is not known to be transmitted from person to person. Therefore, the general public is at extremely low risk,” said IDPH Director Nirav D. Shah, M.D., J.D. “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.”

Seoul virus is carried by wild Norway rats worldwide. People usually become infected when they come in contact with infectious body fluids (blood, saliva, urine) from infected rats or are bitten by them. Most cases in people are reported in Asia. The virus is not spread between people and cannot be transmitted to or from other types of pets.

Seoul virus is not commonly found in the United States, though there have been several reported outbreaks in wild rats. According to the CDC, this is the first known outbreak associated with pet rats in the United States.

Symptoms may include fever, severe headache, back and abdominal pain, chills, blurred vision, redness of the eyes, or rash. In severe cases, infection can also lead to acute renal disease.

In Wisconsin, one of the infected persons had to be hospitalized, but both have since recovered. Five of the six Illinois cases showed no signs of illness.

CDC epidemiologists have been dispatched to Illinois and Wisconsin to assist in the investigation.