Measles kills 18-year-old in PA, 4th death as state outbreak nears 700 cases

A fourth person in Pennsylvania has died of measles, the state health department confirmed Tuesday. The latest death was in an unvaccinated 18-year-old resident of Mifflin County.

In the announcement, the state health department also confirmed a county coroner's report over the weekend of the death of an unvaccinated 40-year-old woman in Jefferson County. The state had previously reported two deaths in Lancaster County, both were in infants—a newborn boy and a 6-week-old girl, both too young to be vaccinated.

According to the Mifflin County coroner, Andrea L. Alcalde, the 18-year-old's cause of death was determined to be acute disseminated encephalomyelitis (ADEM), which is a rare but known severe complication of measles. The condition is characterized by a rapidly progressing autoimmune disorder in which aberrant inflammation from an infection strips away the protective coverings of nerve cells in the brain and spinal cord. Before measles vaccines were widely used, ADEM was commonly associated with measles, though other viral infections can also spur its development.