There is currently a Seoul virus outbreak affecting up to 15 states in the U.S., which is the first of its kind in the nation’s history . Twelve people have been infected thus far: seven from Illinois, three from Wisconsin, one from Indiana , and one from Utah . The remaining 12 states (CO, ND, MN, IA, MO, AR, LA, TN, AL, IN, MI, and SC) have received rats from rat-breeding facilities that are believed to be the source of the infections, and thus have the potential for cases to develop .
The outbreak began in December 2016 when two persons in Wisconsin were hospitalized. The two first cases operated a home-based rat breeding facility, and had purchased rats from animal suppliers in Wisconsin and Illinois prior to becoming infected .
Seoul virus is a type of hantavirus, which is transmitted when humans come in contact with rodent excrement. Seoul virus is transmitted from infected Norway rats (also commonly known as brown rats) to humans through their urine, droppings, or saliva . It is also possible to become infected through “aerosolization”, which occurs when nesting materials or excrement are stirred up by things such as vacuuming or sweeping, and tiny particles containing the virus are released into the air for humans to inhale .
Symptoms in humans are usually mild and typically begin within one to two weeks of exposure. Symptoms may include fever, headache, nausea and chills, back and abdominal pain, blurred vision, inflammation or redness of the eyes, and a rash. In rare cases, hemorrhagic fever with renal syndrome (HFRS) may develop, and an estimated one to two percent of people die as a result of a Seoul virus infection . In the current outbreak, two of the 12 cases have been hospitalized and no deaths have so far been reported .
The Centers for Disease Control and Prevention (CDC) currently recommends blood testing for anyone that experiences illness after handling rats from a facility that has been lab-confirmed to have Seoul virus infection, and encourages providers to do blood testing if a patient reports symptoms consistent with a Seoul virus infection and has a history of rat contact. In addition, the CDC recommends that people who may have potentially infected rats, to not sell, trade, or release their rats . Investigations are currently being conducted by state and local health departments, in partnership with the CDC, to identify the original source of infection, target infected rat populations, and control the outbreak.