Walsh & Hoyt: Epidemiology

Acute disseminated encephalomyelitis previously accounted for about one-third of the cases of acute encephalitis throughout the world; however, with the worldwide discontinuation of vaccinia virus immunization to protect against smallpox, the percentage became significantly reduced. It was reduced even further by the widespread use of attenuated live measles vaccine. In the United States, where mumps and rubella viruses are routinely included with the mandatory measles virus vaccine, a decrease occurred not only in infections caused by these viruses but also in their parainfectious complications. Because of these advances in the control of these viral diseases, ADEM occurs most often throughout the world after a nonspecific upper respiratory tract infection where the etiologic agent is unknown.