Measles is one of the most contagious diseases for humans. It is caused by a paramyxovirus virus, manifesting as a febrile rash illness. The incubation period for measles usually is 10–14 days (range 7–23 days) from exposure to symptom onset. Initial symptoms (prodrome) generally consist of fever, malaise, cough, conjunctivitis, and coryza. The characteristic maculopapular rash appears two to four days after onset of the prodrome. Patients are usually contagious from about four days before rash onset until four days after its appearance.