he Centers for Disease Control and Prevention is casting a wider net looking for people who might have contracted the Seoul virus from infected rats.
The agency said Tuesday the current investigation of eight cases in Wisconsin and Illinois suggests that people in 10 other states may have been exposed to infected rats through the distribution chains of the affected breeding facilities.
The additional states are: Alabama, Arkansas, Colorado, Indiana, Louisiana, Michigan, Minnesota, South Carolina, Tennessee, and Utah.
The rat raising facilities are small “mom and pop”-type operations, Dr. Pierre Rollin, a CDC expert in hemorrhagic diseases, told STAT. The animals are destined to be pets or are sold to be fed to snakes. These are not rats raised for research purposes.
As investigators have interviewed people in affected rat-breeding facilities, it has become clear animals from them have been more widely distributed than was first realized, Rollin said.
The CDC issued an alert to health professionals Tuesday, urging them to be on the lookout for cases of Seoul virus, a type of hantavirus, in people working at an affected facility, or working at breeders that sold rodents to an affected facility.
In fact, the agency said it recommends hantavirus testing be considered when any person has symptoms of Seoul virus infection and has had contact with a rat.
Seoul virus normally causes mild disease and may even trigger symptom-free infection. Symptoms include fever, severe headache, back and abdominal pain, chills, blurred vision, redness of the eyes, or a rash. But some infected people will go on to develop severe infection affecting the kidneys — hemorrhagic fever with renal syndrome — and between 1 percent and 2 percent of those cases are fatal.
Though it is known that wild rats in the United States can carry Seoul virus, this is the first known outbreak of human cases.
Rats shed the virus in their urine, feces, and saliva. People who clean out rat dwellings or who handle or are bitten by infected rats can become infected. People cannot transmit the virus person to person.
The first case came to light in Wisconsin in December, when a rat breeder got sick. A family member who also worked with rats tested positive for the virus as well.
When investigators traced the rats in the breeding operation back to their source, they found six more infected people. The six worked at two different breeding facilities in Illinois.
Of the eight cases seen so far, two were sick enough to require hospitalization, but there have been no deaths to date.