, also known as rubeola, is one of the most contagious infectious diseases, with at least a 90% secondary infection rate in susceptible domestic contacts. It can affect people of all ages, despite being considered primarily a childhood illness. Measles is marked by prodromal fever, cough, coryza, conjunctivitis, and pathognomonic enanthem (ie, Koplik spots), followed by an erythematous maculopapular . Media Gallery * * * Koplik spots in measles. Photograph courtesy of World Health Organization. * * Enanthem of measles (Koplik spots). * * Measles conjunctivitis. * * Face of boy with measles. * * Morbilliform rash. of 5 TablesBack to List Contributor Information and Disclosures Author Selina SP Chen, MD, MPHAssistant Professor of Pediatrics, Department of Internal Medicine, John