Federal health officials have traced the origins of the monkeypox virus in the United States to a shipment of exported African rodents. The national Centers for Disease Control and Prevention confirmed the virus in one Gambian rat, three dormice, and two rope squirrels entering the country April 9.

As a result, the CDC has issued guidance on the quarantine and euthanasia of all animals from the shipment, as well as prairie dogs from the United States that were exposed to the imported species or with other animals suspected to have monkeypox.

Shortly after the monkeypox virus was detected in June, the Department of Health and Human Services banned the sale and display of prairie dogs and six specific African rodent species. Moreover, importation of all rodents from Africa was embargoed.

Six states report monkeypox infections: Wisconsin, Illinois, Indiana, Kansas, Missouri, and Ohio. Infections have been confirmed in 32 people, while 49 possible infections are under investigation. No human deaths are related to the outbreak.

Infected persons had direct or close contact with sick pet prairie dogs, a Gambian rat, or a rabbit that was housed with an ill prairie dog. Person-to-person transmission by contact with lesions has also been reported.

Monkeypox virus is less infectious that the deadly smallpox virus, and people infected with monkeypox virus rarely die as a result of the disease. Some of the infected animals have died, however. The virus incubates in people for about 12 days, but that period can range from four to 20 days.

Animal species susceptible to monkeypox virus include nonhuman primates, rabbits, and some rodents. Person-to-person transmission of monkeypox virus has been reported to occur at a rate of 1 percent to 10 percent.