The Centers for Disease Control and Prevention (CDC) is currently investigating cases of Seoul virus infections in 8 workers from several rat-breeding facilities in Illinois and Wisconsin.

While outbreaks of Seoul virus have been previously reported in wild rats, the virus is not commonly found in the Untied States and this is the first known outbreak associated with pet rats.

In December 2016, a home-based rodent breeder in Wisconsin was hospitalized with symptoms of fever, headache, and others. Upon testing, the CDC confirmed that the infection was caused by Seoul virus of the Hantavirus family of rodent-borne viruses. A close family member who also worked with rodents tested positive for the Seoul virus. An additional six cases of Seoul virus at two Illinois rat breeding facilities were reported after a follow-up investigation at several rat breeders that supplied the original patient’s rats.  

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Seoul virus is transmitted by wild Norway rats across the world. Individuals become infected when they are bit by infected rats or come in contact with infectious body fluids (eg, blood, saliva, urine). Infected rats, however, usually do not appear sick. Seoul virus is not transmitted between humans and cannot be transmitted to or from other types of pets. 

Symptoms of Seoul virus illness may include fever, severe headache, back and abdominal pain, chills, blurred vision, redness of the eyes, or rash; acute renal disease may result in rare cases. The CDC recommends the following strategies to prevent Seoul virus infections and other rodent-borne illnesses: 

  • Wash your hands with soap and running water after touching, feeding, or caring for rodents, or cleaning their habitats. Be sure to assist children with handwashing.
  • Be aware that pet rodents can shed germs that can contaminate surfaces in areas where they live and roam. Make sure rodent enclosures are properly secured and safe, so your pet doesn’t get hurt or contaminate surfaces.
  • Clean and disinfect rodent habitats and supplies outside your home when possible. Never clean rodent habitats or their supplies in the kitchen sink, other food preparation areas, or the bathroom sink.
  • Avoid bites and scratches from rodents. Be cautious with unfamiliar animals, even if they seem friendly. Take precautions when cleaning out rodent cages or areas with rodent urine or droppings.
  • Visit your veterinarian for routine evaluation and care to keep your rodents healthy and to prevent infectious diseases.

Patients with Seoul virus infection are typically given supportive care to treat symptoms. Care may include fluid therapy to maintain blood volume, blood pressure, and electrolyte (sodium, potassium, chloride) levels. Oxygen may also be used as well as appropriate treatment of any secondary infections. In severe cases of kidney failure, dialysis may be required. Ribavirin has been shown to reduce the illness severity and lower deaths related to Seoul virus infections if used very early in the disease.

Any individual who has purchased a rat in the affected areas and is experiencing Seoul virus symptoms should contact their healthcare provider right away. The CDC and its state and local health partners are contacting rodent suppliers to learn more about suppliers for the Wisconsin rat breeder. Health officials are working to ensure infected rats are not distributed further. 

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