Measles is a very contagious disease. When a person has measles, they spread the disease when they cough or sneeze. It spreads so easily you can be infected just by being in the same room as a person who has measles, for up to two hours after that person has left. A person can spread measles to someone else even before they know they are sick with the disease.
Resources for the general public
Resources for child care facilities and schools