Vaccinia

an infectious disease of cattle caused by a poxvirus that may be transmitted to humans by direct contact or deliberate inoculation as a vaccine against smallpox. A pustule develops at the site of infection, usually followed by malaise and fever that last for several days. After 2 weeks the pustule becomes a crust that eventually drops off, leaving a scar. Satellite lesions may occur, and the virus may be spread to other sites by scratching. Individuals with eczema or other preexisting skin disease may develop generalized vaccinia. Rarely, a severe encephalitis follows vaccinia.