DefinitionMeasles is a very contagious (easily spread) illness caused by a virus.Alternative NamesRubeolaCauses, incidence, and risk factorsThe infection is spread by contact with droplets from the nose, mouth, or throat of an infected person. Sneezing and coughing can put contaminated droplets into the air.Those who have had an active measles infection or who have been vaccinated against the measles have immunity to the disease. Before widespread vaccination, measles was so common during childhood that most people became sick with the disease by age 20. The number of measles cases dropped over the last several decades to almost none in the U.S. and Canada. However, rates have started to rise again recently.Some parents do not let their children get vaccinated because of unfounded fears th