WASHINGTON (Reuters) -- An outbreak of monkeypox that has affected 81 people has been traced to a giant Gambian rat and assorted other small rodents imported as pets from Africa, U.S. health officials said on Wednesday.
The Centers for Disease Control and Prevention confirmed monkeypox infection in one Gambian giant rat, three dormice, and two rope squirrels shipped to the United States in April.
"This shipment is believed to be the source of the current U.S. outbreak of monkeypox," the CDC said in a statement.
The animals were kept in close contact with prairie dogs
at a Texas importer. The prairie dogs, native to the American plains but popular as pets, were shipped to Illinois, Indiana, Kansas, Missouri, Ohio, and Wisconsin.
The CDC suspects 81 people were infected by the animals and confirmed 33 cases. There have been no confirmed cases of a person transmitting the disease to another person, although the CDC is investigating several possible incidents, a spokesman said.
"I think we probably are on a downward slope, but we are not ready to call it over yet," CDC spokesman David Daigle said in a telephone interview.
Daigle said 28 people in six states have been vaccinated with the smallpox vaccine, which may help to protect against the worst symptoms of monkeypox.
Monkeypox, a disease related to smallpox, has similar symptoms but is much less deadly. It was mostly seen in central and western Africa until this outbreak.
No one in the United States has died in this monkeypox outbreak. In Africa, it kills about 10 percent of the people who get the disease.
Once the outbreak was confirmed, the CDC and Food and Drug Administration banned the import of all African rodents into the United States and the sale or release of prairie dogs and six types of African rodents.
The CDC said it was advising pet shops, pet owners, and veterinarians about how to prevent further spread of the virus. All animals quarantined in connection with this outbreak are to be destroyed.
"There is concern that monkeypox might have spread more broadly to other animals housed together in pet stores
, other animal facilities, and 'pet swap' meets," said the CDC, warning pet owners to keep an eye out for symptoms of the disease in animals.
These include fever, cough, discharge, cloudiness or crustiness in the eyes, swelling in the limbs from enlarged lymph nodes, or a blister-like rash.
"The goal is to protect people, pets and wildlife in the United States by preventing the monkeypox virus from spreading or becoming established permanently," said Dr. Martin Cetron, deputy director of the CDC's global migration and quarantine programs.
The CDC also warned owners of prairie dogs not to release the animals into the wild, where the disease could spread unchecked. Nor should pet owners destroy or dispose of the rodents themselves.
Daigle said some state health departments may trap wild prairie dogs to make sure monkeypox has not escaped into the wild. "That is a great fear -- that it could become endemic (permanent) in the United States," Daigle said.
Monkeypox belongs to a group of viruses that includes the smallpox virus and the vaccinia virus used in the smallpox vaccine. It was first seen in 1958 in laboratory monkeys and later found in people in Africa after smallpox was eradicated.
"Rats, mice, and rabbits can get monkeypox, too," the CDC said.