In 2003, the Wisconsin Division of Public Health conducted an investigation of state residents who became ill after having contact with prairie dogs. The cases appeared in May and June of 2003, and symptoms in the human cases included: fever, cough, rash, and swollen lymph nodes. CDC laboratory test results indicated that the cause of the human illness was Monkeypox, an orthopox virus that could be transmitted by prairie dogs. These prairie dogs became infected when they were exposed to imported African rodents that were carrying the virus.
The Division of Public Health, working with local partners, offered smallpox vaccinations to individuals involved in this outbreak who had exposure to a sick animal or an individual who showed symptoms of monkeypox illness.
Human monkeypox is a rare zoonotic viral disease (zoonotic means a disease of animals, such as rabies, that can be transmitted to humans), known to occur primarily in the rain forest countries of central and west Africa. In humans, the illness produces a vesicular and pustular rash similar to that of smallpox. Limited person-to-person spread of infection has been reported in disease-endemic areas in Africa.
The 2003 outbreak was the first known occurrence of monkeypox in the western hemisphere. There have been no additional cases since 2003.