CDC Assisting Illinois and Wisconsin Investigation of Seoul Virus Outbreak Associated with Home-based Rat-Breeding Facilities

Experts from the Centers for Disease Control and Prevention are working with the Illinois Department of Health and the Wisconsin Department of Health Services to investigate cases of Seoul virus infections among eight people who worked at several rat-breeding facilities in the two states. Seoul virus is not commonly found in the United States, though there have been several reported outbreaks in wild rats. This is the first known outbreak associated with pet rats in the United States.

A home-based rodent breeder in Wisconsin was hospitalized in December 2016 with fever, headache, and other symptoms. CDC tested a blood specimen and confirmed that the infection was caused by Seoul virus, a member of the Hantavirus family of rodent-borne viruses. A close family member who also worked with rodents also tested positive for Seoul virus. Both people have recovered. A follow-up investigation at several rat breeders that supplied the initial patient’s rats revealed an additional six cases of Seoul virus at two Illinois rat breeding facilities.

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. Rats infected with Seoul virus typically do not appear sick.

CDC has deployed two epidemiologists to work with local and state health authorities to determine if any customers who bought rats have become ill. Human and animal health officials are working together to make sure infected rats are not distributed further. CDC and its state and local health partners are reaching out to rodent suppliers to learn more about suppliers for the Wisconsin rat breeder. These efforts will help determine how the two individuals in Wisconsin were initially exposed to Seoul virus and allow public health officials to take actions to prevent future spread of the virus. CDC staff will also provide laboratory testing for blood samples from people who may have come in contact with rats from the affected rat breeders.

Though Seoul virus is in the Hantavirus family, it produces a milder illness than some other Hantaviruses. Symptoms may include fever, severe headache, back and abdominal pain, chills, blurred vision, redness of the eyes, or rash.  In rare cases, infection can also lead to acute renal disease.  However, not all people infected with the virus experience symptoms. Most people infected with Seoul virus recover.

People in Illinois and Wisconsin who are concerned that they have purchased or come in contact with rats from the affected breeders should contact their local or state health departments. Anyone who recently purchased a rat in the affected areas and experiences Seoul virus symptoms should contact their healthcare provider immediately.

To prevent infections from Seoul virus and other diseases carried by rats, people should:

• 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.

If bitten by a rodent: 

• Wash the wound with warm soapy water immediately. Even healthy pets can carry germs.

Seek medical attention if: 

• Pet appears sick.
• Your wound is serious.
• Your wound becomes red, painful, warm, or swollen.
• Your last tetanus shot was more than 5 years ago.
• You develop sudden fever or flu-like illness in 1-2 weeks after being bitten

Tell your healthcare provider that you have been around pet rodents, whether at home or away from the home, especially if you are sick or have been bitten or scratched. 

For more information on Seoul virus, please visit https://www.cdc.gov/hantavirus/outbreaks/seoul-virus/index.html .

For more information, please visit:www.cdc.gov/healthypets or https://www.cdc.gov/healthypets/resources/pet-rodents-8x11-508.pdf .

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U.S. DEPARTMENT OF HEALTH AND HUMAN SERVICES