In a follow-up on the first ever known Seoul virus outbreak in the United States, the Centers for Disease Control and Prevention (CDC) as of Jan. 31 reports 10 confirmed cases in Wisconsin (3) and Illinois (7) who were exposed to infected rats in several rat-breeding facilities in those two states.


In addition, ten additional states (Alabama, Arkansas, Colorado, Indiana, Louisiana, Michigan, Minnesota, Missouri, South Carolina, Tennessee and Utah) have been notified that that their residents may have infected rats.

CDC is working with state health departments and others to investigate the outbreak of Seoul virus infections in pet rodents and humans. They are working to trace shipments and transport of rats, some of which may be 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.

According to the CDC, this is the first known outbreak associated with pet rats in the United States.

How concerning is that point? I asked Columbia University virologist, Dr Vincent Racaniello that exact question on the Outbreak News This Week Radio Show and he replied, “Well yea I think that we’re always seeing new viruses popping up like this, the question is, has it been around before and we just didn’t recognize them?

“I think people have always had pet rats and maybe we didn’t recognize the syndrome before or maybe this is really something new, we’ll see. I do hope that we could use ways of diagnosing the rats to make sure these ratteries are virus free.”

What about testing rats for Seoul virus? The CDC says Seoul virus testing can be done on live rats by taking a small blood sample and testing it. CDC performs serology tests looking for antibodies and PCR tests to detect evidence of virus genetic material.

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.

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.

Symptoms may include fever, severe headache, back and abdominal pain, chills, blurred vision, redness of the eyes, or rash. In severe cases, infection can also lead to acute renal disease.