Animals and animal byproducts from infected areas are prohibited entry into the United States, which has remained free of the disease since 1929. Extremely contagious, these viruses are spread through physical contact by animals, people, or materials. They can also be airborne, traveling 30 miles in the wind. Humans are very resistant to these viruses. Infected animals, however, may not show signs of the disease for months.
Vaccines exist, but new strains of the virus quickly render vaccines ineffective.
Susceptible and infected animals are typically slaughtered and the carcasses burned to stop the disease. The European Commission has temporarily banned all livestock imports from Britain. To keep people from spreading the disease, major sporting events and parades have been canceled or postponed, countryside walks and fishing banned, and all 11 national parks in England and Wales closed. Continental countries and the United States have begun requiring visitors from Great Britain to walk through tubs or across mats of disinfectant to kill any virus that may be present on their shoes.