Measles is an acute viral illness caused by paramyxovirus, genus Morbillivirus. This virus causes a rash all over the body. It also causes fever, runny nose and cough. About 1 out of 10 children with measles also get an ear infection, and up to 1 out of 20 get pneumonia. About 1 out of 1,000 get encephalitis, and 1 or 2 out of 1,000 die. Measles can also make a pregnant woman have a miscarriage or give birth prematurely.
Measles spreads through the air by breathing, coughing or sneezing. The incubation period of measles, from exposure to prodrome averages 10–12 days. From exposure to rash onset averages 14 days (range, 7–18 days). It is so contagious that any child who is exposed to it and is not immune will probably get the disease. Before measles vaccine, nearly all children got measles by the time they were 15. Each year about 450 people died because of measles, 48,000 were hospitalized, 7,000 had seizures, and about 1,000 suffered permanent brain damage or deafness.