Postinfectious measles encephalitis is an autoimmune response characterized by inflammation and demyelination that is triggered by the measles virus. The measles virus is transmitted through respiratory droplets and is thought to have impacted civilizations as early as 4000 B.C. A young Danish physician, Peter L. Panum, however, is credited with much of the information that is now known about measles, including the highly contagious nature of the disease. Panum was sent to the Faroe Islands in the mid- 1800s to assist with a large-scale measles outbreak and discovered that measles have an incubation period of about 14 days. In most cases, individuals begin to show signs of improvement about five days after the measles rash appears. It is not clear how the measles virus triggers the autoimmune reaction that causes encephalomyelitis. However, when this occurs there is considerable neurologic involvement, and prior to the introduction of the measles vaccine, it was the most common cause of neurological disability. Encephalitis-associated symptoms include fever, headache, seizures, and coma. It has been estimated that 50% of individuals who contract post- infectious measles encephalitis develop seizures and nearly 100% show impaired consciousness during the episode. Other neurologic-related sequelae include intellectual deterioration, hemiparesis, paraplegia, and ataxia.