The Centers for Disease Control and Prevention (CDC) today issued an official health advisory regarding confirmed cases of human illness caused by Seoul virus, a member of the hantavirus group of rodent-borne viruses. Two confirmed cases occurred in Wisconsin residents who cared for domestic rats at a rat-breeding facility in northeastern Wisconsin. Other cases have been confirmed in Illinois and investigations underway have identified distribution chains in other states that may require additional investigations.
Human infections with this virus are rare in the United States. Individuals who become infected with Seoul virus often exhibit relatively mild or no symptoms, but some will develop a form of hemorrhagic fever with renal syndrome (HFRS) that can result in death in approximately 1 percent to 2 percent of cases. Although serologic studies have indicated the presence of Seoul virus in wild rats in the United States, this is the first known outbreak associated with pet rats in the United States.
The CDC and officials at the Wisconsin Division of Health Services (DHS) Department of Public Health currently recommend testing all individuals who report recent or current illness after (1) handling rats from a facility with Seoul virus infection that was confirmed by laboratory testing (either rat or human), or (2) handling rats from a facility that sold rats to a facility with Seoul virus infection. Testing also is offered to those without illness, but (1) who are reporting exposure to rats from a facility with Seoul virus infection that was confirmed by laboratory testing, or (2) who are reporting exposure to rats from a facility that sold rats to a facility with Seoul virus infection, but where no illness has been reported.
In general, health officials recommend consideration of hantavirus testing in all individuals with symptoms of Seoul virus infection and rat contact, even if the rat was not associated with a facility where a confirmed infection in a rat or human was reported.
In the United States, hantavirus infections in people are notifiable conditions. Health care professionals who suspect hantavirus infection in a patient should contact their state or local health department.