A mother and her daughter in Tennessee were infected with a virus rarely seen in the United States, and the culprit seems to be pet rats.

The two women tested positive for the Seoul virus, according to a new report, published today (Oct. 12) by the Centers for Disease Control and Prevention (CDC). The Seoul virus is part of the Hantavirus family, a group of viruses that typically infect rodents.

The CDC reported in January that there was an outbreak of the virus among rat breeders and owners in Illinois and Wisconsin; that same month, the Tennessee Department of Health was notified of an individual with pet rats from one of the Illinois breeders with infected rats, according to the new report. [10 Deadly Diseases That Hopped Across Species]

In fact, the owner of the pet rats, an 18-year-old, had gotten sick in December 2016 with an "unspecified viral illness," the researchers said. She recovered fully from the virus without treatment. A test on a preserved sample of her blood that had been drawn when she was sick revealed that she had been infected with the Seoul virus.

The teenager didn't let health officials test her pet rats for the virus, but the officials presumed that the rodents also had the virus. As such, the officials recommended that the rats be euthanized. Once again, the teen refused. In response, the Tennessee Department of Health prohibited the teen from removing the rats from her home, essentially quarantining the pets. In addition, they educated the teen and her family about the best ways to avoid infection, which include avoiding contact with rodent urine, droppings, saliva and nesting material, according to the report.

But in April, the teen's 38-year-old mother got sick, too. She went to the emergency room with symptoms including a very high fever of 104.5 degrees Fahrenheit (40.3 degrees Celsius), shortness of breath, fatigue and lack of appetite, the report said. A blood test revealed that she had the Seoul virus. The mother told doctors that she had cleaned up rodent droppings from a bathtub about three weeks before she got sick.

The Seoul virus

The Seoul virus infects brown Norway rats (Rattus norvegicus), which are found worldwide, according to the report. The virus can spread easily between rats, and can also be passed from rats to humans, according to the CDC. As of January, 17 confirmed cases of the Seoul virus in people in the U.S. have been linked to rats from breeders in Illinois, the report said.

However, the virus cannot spread from human to human, according to the CDC.

Severe infections with the Seoul virus can cause a disease called hemorrhagic fever with renal syndrome, which includes symptoms such as internal bleeding and kidney problems, the CDC says. Most people who are infected with the Seoul virus, however, experience mild or even no symptoms, and the death rate for the disease is approximately 1 or 2 percent, the CDC says.

Indeed, the Seoul virus is less severe than another form of the hantavirus, called the Sin Nombre virus, according to the CDC. The Sin Nombre virus is spread by the deer mouse (Peromyscus maniculatus), and it causes a condition called hantavirus pulmonary syndrome. These infections can cause severe breathing difficulties that require hospitalization, and the death rate for the disease is about 38 percent, the CDC says.

Originally published on Live Science.