A pet rat in a Pennsylvania home-based breeding facility has tested positive for the Seoul virus, state Health Secretary Karen Murphy announced Thursday.

No human infections of the virus have been confirmed in Pennsylvania, but the federal Centers for Disease Control and Prevention report there have been 13 known human infections nationwide from the outbreak. Last month, the CDC announced eight people who worked in several breeding facilities in Illinois and Wisconsin had gotten infected. It is the first U.S. outbreak involving pet rats.

The Pennsylvania rat was bought from a Tennessee breeding facility with confirmed Seoul flu infections. The rats at the Pennsylvania facility were euthanized to prevent further spread of the disease.

"If you have pet rats you feel could be infected, or if you or your loved ones have been in contact with pet rats and have any symptom of Seoul virus, you should contact the department at 1-877-PA-HEALTH," Murphy said.

State health department spokeswoman April Hutcheson said pet rats can be given a blood test if they are suspected of carrying the virus. She declined to say where in the state the infected rat was because she said the investigation is ongoing.

The Seoul virus is found worldwide. It is carried and spread by rodents, specifically the brown or Norway rat. People can become infected after coming contact with infected rats' urine, droppings or saliva.

Human symptoms are often relatively mild and include fever, chills, nausea, headache, back or abdominal pain, rash, blurred vision, red eyes or flushing of the face.

In rare cases, infections can lead to hemorrhagic fever with renal syndrome. The syndrome's symptoms includes acute shock or kidney failure and low blood pressure.  There is no effective treatment for the virus.