Eight people who worked at rat-breeding facilities in Illinois and Wisconsin contracted Seoul virus but have since recovered.
The Centers for Disease Control and Prevention (CDC) confirmed Friday that pet rats were the source of an outbreak of Seoul virus in two midwestern states.
The Seoul virus is a rodent-borne hantavirus that can cause a form of hemorrhagic fever. Symptoms of the virus typically appear within 1 to 2 weeks after contact with an infected rat, but can take up to 8 weeks. Symptoms include fever, chills, nausea, pink eye—type infections, and abdominal pain. In very serious cases, the condition can progress to hantavirus pulmonary syndrome, which begins with fever, severe aches, and fatigue and could potentially turn fatal.
Eight people who worked at multiple rat-breeding facilities in Illinois and Wisconsin have been diagnosed with the virus. The first two cases were reported in a home breeding facility in Wisconsin in December 2016; follow-up investigation led to six additional cases from two breeding facilities in Illinois. All of the affected individuals have recovered.
The Illinois Department of Public Health said that of the six people who tested positive for Seoul virus in that state, only one experienced any illness or symptoms.
This is the first known outbreak associated with pet rats in the United States—most cases have been reported in Asia.
Wild Norway rats are the culprits who have carried the Seoul virus across the globe since the late 1700s. Most infected rats don’t show clinical signs.
Infection is transmitted through bodily fluids such as blood, saliva, or urine from an infected rat, or following a bite from an infected rat. The virus cannot be transferred between people or from other types of pets, according to the CDC.
To track where other possible infections may have occurred, the CDC is working to determine where the infected rats came from and where they may have been sent. Officials believe the virus has not spread any farther than the areas already under investigation. Anyone who is concerned that they may have purchased a rat from an affected breeding facility should contact their local or state health department. People who experience symptoms of the virus should contact their healthcare provider immediately.
To prevent Seoul virus infections, pet rat owners should take the following precautions with their animals:
If bitten or scratched by a pet rat, the owner should wash the wound with warm, soapy water and visit a veterinarian if the injury becomes worse or if the rat seems ill.
Jennifer McQuiston, DVM, MS (CAPT, USPHS), deputy director of the CDC’s Division of High Consequence Pathogens and Pathology, said, "Our general recommendation is that anybody who has a pet rodent should be cognizant of good pet care behavior.”