The cause of measles is a very contagious virus, which lives in the mucus in the nose and throat of an infected child or adult. That child or adult is contagious from four days before the rash appears to four days after.

When someone with measles coughs, sneezes or talks, infected droplets spray into the air, where other people can inhale them. The infected droplets may also land on a surface, where they remain active and contagious for several hours. You can contract the virus by putting your fingers in your mouth or nose or rubbing your eyes after touching the infected surface.

Jun. 01, 2011