Measles is a viral infection of the respiratory tract and the skin. It is one of the most contagious diseases known. Measles was once very common, but a vaccine has made it much more rare.
Measles is spread by direct contact with a person who has measles. It is spread by contaminated droplets that are breathed or coughed into the air from the contagious person.
Measles is caused by the rubeola virus. People who live in crowded or unsanitary conditions are more likely to get measles.