Jun 11, 2003 (CIDRAP News) – To contain the emerging monkeypox outbreak, federal health authorities today recommended smallpox vaccination for people potentially exposed to the disease and acted to freeze the movement of pets that may carry it.
The steps were announced as the number of monkeypox cases under investigation increased to 54, including 23 in Indiana, 20 in Wisconsin, 10 in Illinois, and 1 in New Jersey. Nine cases have been confirmed, according to the Centers for Disease Control and Prevention (CDC).
The CDC recommended smallpox shots for people investigating monkeypox cases, those caring for infected people and animals, and household contacts of monkeypox patients. CDC Deputy Director Dr. David Fleming said the vaccine has been shown to be about 85% effective in preventing monkeypox, which resembles smallpox but is less infectious and lethal.
Further, because of evidence that an imported Gambian giant rat brought monkeypox to the United States, Secretary of Health and Human Services (HHS) Tommy Thompson announced an immediate ban on importation of all African rodents. He also banned the distribution, sale, transportation, and release of prairie dogs—which are believed to have carried monkeypox to humans—and six other rodent species.
In a news release on the vaccination recommendation, CDC Director Julie Gerberding stated, "Monkeypox can be a serious illness, and it has not been previously seen in humans in this hemisphere. CDC and a team of expert advisors carefully weighed the risk of smallpox vaccination against the risks posed by exposure to monkeypox infection in arriving at this important decision."
For people who have an increased risk of smallpox vaccine side effects, such as pregnant women and those who have eczema, a decision for smallpox vaccination should await confirmation of suspected cases of monkeypox to which they were exposed, the CDC said.
In announcing the action on rodents, Thompson said, "Today's action is an important step we must take in order to help prevent further spread of this virus." Besides prairie dogs, the ban applies to tree squirrels, rope squirrels, dormice, Gambian giant pouched rats, brush-tailed porcupines, and striped mice.
The HHS statement also said anyone who has acquired any of these animals since Apr 15 should monitor their own health and that of the animal and contact their physician or a veterinarian if symptoms appear. Any sick animal should be taken to a veterinarian who has been alerted in advance, officials said.
Because of the risk of giving monkeypox a permanent foothold in the Americas, the CDC said, "CDC strongly cautions pet owners not to release these animals into the wild but to contact their state health departments for guidance if there is any concern about the health of an exotic rodent or prairie dog acquired as a pet after April 15 of this year."
The CDC said it is not recommending smallpox vaccination for veterinarians, veterinary staff, or animal control officiers who have not been exposed to the disease. But such personnel should take steps to prevent contact or airborne transmission of the virus if they investigate or treat sick animals, officials said.
Smallpox shots can be given up to 14 days after exposure to monkeypox, the CDC said. Because the vaccine is not approved for monkeypox, the vaccine for this use will be distributed under special Food and Drug Administration (FDA) procedures to allow emergency use with informed consent from the patient and approval by an institutional review board, the agency said.
During a telephone news briefing today, Fleming said he expects that the number of people vaccinated to prevent monkeypox will be "relatively modest." He and other officials said recent bioterrorism preparedness efforts, including the smallpox vaccination program of the past 5 months, will make it easier to vaccinate people for this new purpose. "We do have providers in the states who are prepared to go out and deliver this vaccine," Fleming said. "The start-up time has been significantly shortened."
The CDC expects that public health personnel will administer the smallpox shots, he said, adding, "There's a trained work force as a result of the smallpox vaccination program."
CDC officials said earlier this week that monkeypox may have spread to prairie dogs from a Gambian giant rat at a northern Illinois animal distributor's establishment. Today Fleming said that a shipment of African rodents possibly carrying the disease went to Texas and that prairie dogs may have been exposed to the disease there before they were shipped to the Midwest.
Monkeypox has not yet been confirmed in Gambian giant rats or other rodents imported from Africa, Fleming said. The CDC is doing a trace-back investigation of whether any other pets, such as hamsters, may have been exposed to monkeypox in pet stores, he noted.
He said people who have prairie dogs or other rodents showing possible signs of monkeypox are strongly encouraged to contact their veterinarian or public health authorities so the animals can be examined. "For animals that do have monkeypox, we are recommending euthanasia," he said. "The key message is that they should not be released into the wild."
Human monkeypox occurs mainly in central and West Africa and has never been reported in the Western Hemisphere before, according to the CDC. The disease has had a fatality rate of 1% to 10% in Africa, but there have been no deaths in the current outbreak.
CDC news release about smallpox vaccination
HHS news release about the ban on importation, sale, and transportation of rodents