FAQs: Seoul virus

Yes. Seoul virus is a member of the hantavirus family of rodent-borne viruses. This family also includes Sin Nombre virus, which is the most common hantavirus causing disease in the United States.  Most hantaviruses have only one or two rodent species as their natural host.  For Seoul virus, the natural host is the Norway rat (Rattus norvegicus) and the black rat (Rattus rattus), whereas for Sin Nombre it’s the deer mouse (Peromyscus maniculatus). In the rodents that carry them, these viruses don’t cause disease, but do cause life-long infection and shedding of the virus.  These viruses can occasionally spill over into other species of rodents, but they don’t cause chronic virus infections and shedding.

The severe disease associated with Sin Nombre virus infections is called hantavirus pulmonary syndrome (HPS). Most HPS infections lead to fever and body aches, progressing to severe breathing difficulties that frequently require hospitalization. Death occurs in approximately 38% of cases (or 38  of every 100 patients).  In contrast, the severe disease associated with Seoul virus is called hemorrhagic fever with renal syndrome (HFRS).  Most people who get infected with Seoul virus experience mild or even no symptoms.  However, in the severe form of the disease, patients can exhibit bleeding and kidney involvement, and death occurs in approximately 1-2% of cases (or 1-2 of every 100 sick individuals).

CDC worked with state health departments and others to investigate an outbreak of Seoul virus infections in pet rodents and humans. CDC and its partners traced shipments and transport of rats, some of which were infected with Seoul virus, to better understand how the virus entered the pet trade, and to interrupt transmission of Seoul virus to other rats or people.

While Seoul virus infection in humans is generally considered less severe than some other types of hantavirus infections, it can still cause a severe illness in some cases. Some people may develop a severe form of infection known as hemorrhagic fever with renal syndrome (HFRS), and an estimated 1-2% of people may die after being infected with Seoul virus. Because there is presently no effective treatment for Seoul virus infection, preventing infections in people is important.

Seoul virus diagnostic testing can be done on live rats by taking a small blood sample and testing it in a laboratory. Rats do not have to be euthanized to collect a blood sample. The blood sample is sent to CDC or to another laboratory to perform the diagnostic test for Seoul virus infection. CDC and the other lab perform tests looking for antibodies (serologic tests) and/or evidence of virus genetic material [by polymerase chain reaction (PCR)]. A positive result means that the rat has been infected with Seoul virus and is presumed to pose a risk for transmitting the virus to other rats or to people. Infected rats are believed to remain infectious for life with permanent or intermittent shedding of virus. A negative result means there is no evidence of Seoul virus infection in the rat at the time of the sampling.

State and local departments of health are reaching out to breeders and owners of rats from suspected or confirmed facilities. Teams working with the state department of health will visit suspected facilities, and—working with the owners—will take blood samples for testing. Owners of rats that are not linked to a confirmed facility but who want their rats to be tested may choose to do so independently through commercial laboratories.

Yes. Several commercial laboratories offer testing for Seoul virus. The IDEXX* serologic (antibody) test (Opti-Spot™) and molecular (PCR) test for Seoul virus in rats yield results closely similar to those for CDC’s tests for Seoul virus in rats. The Charles River Laboratories serologic test (EZ-Spot®) is presently being validated by CDC. CDC will continue to work closely with IDEXX and Charles River Laboratories to compare serologic and molecular results for Seoul virus. CDC continues to notify departments of health in the affected states regarding the findings and will be reaching out to pet rat owners and breeders through clubs, forums, and conference calls. Serologic and molecular testing of newly arriving rats can be effective tools to prevent introduction of infected rats into non-infected colonies. Owners and breeders may wish to seek proof of a rodent’s infection status prior to admitting new animals into existing colonies.

*Names of commercial companies are provided for information purposes only and do not constitute an endorsement by CDC or the Department of Health and Human Services.

Serologic testing is the most accurate and sensitive test for Seoul virus. The accuracy of PCR testing as a screening tool is not yet established. Thus, negative results from PCR testing of blood, urine, fecal pellets, bedding, or organs should not be interpreted to mean that a rat is not infected with Seoul virus.

Seoul virus is a type of hantavirus. People that become infected with this virus often exhibit relatively mild or no disease but some will develop a form of hemorrhagic fever with renal syndrome (HFRS) with death in approximately 1-2% of cases (1 to 2 persons in 100 people).

Seoul virus is found worldwide. It is carried and spread by rodents, specifically the brown or Norway rat (Rattus norvegicus). The virus has been found in both pet rats and wild rat populations around the world.

People can become infected with this virus after coming in contact with urine, droppings, or saliva of infected rodents. When fresh rodent urine, droppings, or nesting materials are stirred up (for example, when vacuuming or sweeping), tiny particles containing the virus get into the air. This process is known as “aerosolization”. You may become infected when you breathe in these contaminated materials. You may also become infected when the urine or these other materials containing the virus get directly into a cut or other broken skin or into your eyes, nose, or mouth. In addition, people who work with live rodents can get the Seoul virus through bites from infected animals.

Seoul virus is not known to be spread from person to person.

When you get infected with Seoul virus, you may have the following symptoms:

  • Fever
  • Headache
  • Back and abdominal pain
  • Chills
  • Nausea
  • Blurred vision
  • Flushing of the face
  • Inflammation or redness of the eyes
  • Rash

Symptoms of the illness caused by Seoul virus usually begin within 1 to 2 weeks after contact with infectious material. Rarely, it may take up to 8 weeks to develop symptoms.

In rare cases, infection can also lead to a type of acute renal disease called Hemorrhagic Fever with Renal Syndrome (HFRS), which might include low blood pressure, acute shock, and acute kidney failure. However, Seoul virus infections are usually moderate and the vast majority of patients survive. Complete recovery can take weeks or months. Some people do not develop symptoms at all or have very mild symptoms.

Several laboratory tests of blood and body tissues are used to confirm a diagnosis of Seoul virus infection in patients suspected to have an infection.

Supportive care is given to patients with Seoul virus infections. Care includes fluid therapy by giving the patient liquids directly into the vein to maintain blood volume, blood pressure, and electrolyte (sodium, potassium, chloride) levels. Oxygen mask may also be used as well as appropriate treatment of any secondary infections. Dialysis may be required in severe cases of kidney failure. Ribavirin, an antiviral drug, has been shown to reduce the illness severity and lower deaths related to Seoul virus infections if used very early in the disease.

Avoiding contact with rats and rodent control are key for preventing Seoul virus infections. Rodents near human communities should be controlled, and rodents should be excluded from homes. You should avoid contact with rodent urine, droppings, saliva, and nesting materials. It is important to know how to safely clean up after rodents.

Seoul virus is shed in the urine, feces, and saliva of recently infected rats. Rats can become infected with Seoul virus through wounding or biting other rats and after coming in contact with the urine and feces of infected rats.

Rats do not show symptoms of disease when they are infected with Seoul virus. Rats that may have come from a facility where rats have been confirmed with infection can be tested for evidence of viral infection in a laboratory. Once infected, rats can continue to shed virus throughout their lives, potentially infecting both other rats and humans.

Contact Information

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