Unusual Rat Virus Strikes 8 People in Illinois and Wisconsin

rat, pet rat
(Image credit: George Dolgikh | Shutterstock.com)

A virus rarely seen in the United States recently infected eight people in Wisconsin and Illinois who were working in facilities where pet rats are bred, according to the Centers for Disease Control and Prevention (CDC).

Authorities first became aware of the infections when two people in Wisconsin who operated a rat-breeding facility fell ill in December 2016, with one going to the hospital. Both breeders tested positive for Seoul virus, which is part of the Hantavirus family, a group of viruses that typically infect rodents, the CDC said.

Health officials then discovered that the Wisconsin breeders had purchased rats from two rat-breeding facilities in Illinois, and tests showed that six people who worked at the Illinois facilities were infected with the same virus. [10 Deadly Diseases That Hopped Across Species]

The Seoul virus is known to infect a species of rat called the Norway rat (also known as the brown rat) all over the world. Sometimes, people can catch Seoul virus from rats. So far, most human cases of Seoul virus have occurred in Asia. This is the first time that human Seoul virus cases have been linked with pet rats in the United States, the CDC said.

People become infected with Seoul virus when they are bitten by infected rats, or when they come into contact with the blood, saliva or urine of infected rats, the agency said.

The virus cannot spread from person to person, and "therefore, the general public is at extremely low risk," from these cases, Dr. Nirav Shah, director of the Illinois Department of Public Health (IDPH), said in a statement. "Out of an abundance of caution, we want to let the public know in the event they have recently purchased rats from an affected facility and become ill."

The CDC is working to determine if anyone else who bought the rats has become infected with Seoul virus, and to make sure that any rats that are infected are not distributed from the facilities, the agency said.

People who become infected with the Seoul virus can develop fever, severe headaches, back and abdominal pain, chills, blurred vision, red eyes, or a rash, the CDC said. But some people infected with the virus don't show any symptoms. All eight people infected in the current outbreak have recovered, and five out of the six people in Illinois who tested positive for the virus did not show symptoms, the IDPH said. Rats infected with the virus do not typically show symptoms. [Sting, Bite & Destroy: Nature's 10 Biggest Pests]

People who may have purchased rats from the affected breeders should contact their local state or health departments, the CDC said.

To avoid catching an infection from rats, the CDC said that people can take the following precautions with their pets:

  • Wash your hands after touching or feeding pet rats, or cleaning their cages.
  • Make sure pet rats are properly secured (in a cage) so they don't contaminate surfaces in your home.
  • If possible, clean rodent cages and rodent pet supplies outside of your house, and never clean the animals' cages or supplies in your kitchen or other areas where you prepare food.
  • Avoid bites and scratches from rodents.
  • Take your pet to a veterinarian for routine care to keep the animal healthy and disease-free.

Original article on Live Science.

Rachael Rettner

Rachael is a Live Science contributor, and was a former channel editor and senior writer for Live Science between 2010 and 2022. She has a master's degree in journalism from New York University's Science, Health and Environmental Reporting Program. She also holds a B.S. in molecular biology and an M.S. in biology from the University of California, San Diego. Her work has appeared in Scienceline, The Washington Post and Scientific American.