FRIDAY, July 15, 2005 (HealthDay News) -- The outbreak of monkeypox that occurred in the United States in the summer of 2003 didn't cause any deaths because the strain of virus that caused the outbreak is the least virulent of two known strains of monkeypox, researchers report.
During the outbreak, health officials counted 72 confirmed or suspected cases of human monkeypox, but no deaths. The disease usually kills about 10 percent of infected people.
"We have at least two biological strains of monkeypox virus -- one on the west coast of Africa, and the other in the Congo basin. The 2003 outbreak in the United States was from West Africa. If it had come from the Congo, we might have had a bigger problem on our hands and very well might have seen patient deaths," study senior author Mark Buller of Saint Louis University Health Sciences Center, said in a prepared statement.
Monkeypox belongs to a family of viruses that causes human smallpox, cowpox and camelpox. Monkeypox symptoms include fever, respiratory problems, and pus-filled blisters on the body. Monkeypox is a zoonosis -- an animal disease that can be transmitted to humans.
Recent studies suggest that cases of monkeypox in Africa are on the rise due to human encroachment into the habitats of animals that carry the virus, Buller said.
The U.S. outbreak was caused by a shipment of West African rodents imported for the pet trade. At a pet distribution center, the African rodents infected prairie dogs that were sold as pets.
The findings are reported in the July issue of the journal Virology.
The U.S. Centers for Disease Control and Prevention has more about monkeypox.