Koplik's spots are pathognomonic for measles. The measles virus is a paramyxovirus. In industrialized countries, vaccination has reduced the impoance of this childhood infection (although U.S. incidence increased in 1989 and 1990). In developing countries, however, measles is a major killer of young children. In America, most states now require proof of immunity before school enrollment, and this has reduced the incidence of disease Reference: Ananthanarayan and Paniker&;s Textbook of Microbiology Tenth edition