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At least eight people who breed pet rats have been infected with an unusual virus called Seoul virus, state and federal health officials said Friday.

It’s a type of hantavirus, a respiratory infection spread in rodent droppings. Eight people in Illinois and Wisconsin have been diagnosed, and some were sick enough to need hospital care, the Centers for Disease Control and Prevention said.

Be sure to wash your hands after you tickle your pet rat, the CDC cautions after 8 people got infected with Seoul virus

“A home-based rodent breeder in Wisconsin was hospitalized in December 2016 with fever, headache and other symptoms,” the CDC said in a statement.

“CDC tested a blood specimen and confirmed that the infection was caused by Seoul virus, a member of the Hantavirus family of rodent-borne viruses. A close family member who also worked with rodents also tested positive for Seoul virus. Both people have recovered.”

Six more cases have been reported since then, the CDC said.

Hantaviruses were only identified in 1993. An outbreak of hantavirus in Yosemite National Park in 2012 killed three campers.

“Symptoms may include fever, severe headache, back and abdominal pain, chills, blurred vision, redness of the eyes, or rash."

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The first cases were so mystifying that they were called Sin Nombre virus — Spanish for “the virus without a name.” The first known victim was a strapping young New Mexico man who died despite efforts to save him.

Seoul virus is one of the less dangerous strains of hantavirus, the CDC said. “Though Seoul virus is in the hantavirus family, it produces a milder illness than some other hantaviruses.”

“Symptoms may include fever, severe headache, back and abdominal pain, chills, blurred vision, redness of the eyes, or rash. In rare cases, infection can also lead to acute renal disease," the CDC added. "However, not all people infected with the virus experience symptoms. Most people infected with Seoul virus recover.”

Related: Exotic Pets Bring Health Risks

Everyone should wash hands after touching any rodent, even pets, the CDC advised.

“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. Most cases in people are reported in Asia,” the CDC said.

“The virus is not spread between people and cannot be transmitted to or from other types of pets. Rats infected with Seoul virus typically do not appear sick.”

People are infected when they breathe in dust contaminated with rodent droppings or urine.

"Rats infected with Seoul virus typically do not appear sick.”

There’s no cure, but a generic antiviral drug called ribavirin may help prevent the worst symptoms.

There could be more cases, state health officials said.

“Because rats from ratteries are sold to and swapped among individuals, we are working with local health departments and the Centers for Disease and Prevention (CDC) to determine if there are additional cases,” said Karen McKeown of Wisconsin’s state health department.

“Be aware that pet rodents can shed germs that can contaminate surfaces in areas where they live and roam. Make sure rodent enclosures are properly secured and safe, so your pet doesn’t get hurt or contaminate surfaces,” the CDC advised.