What causes measles?
Measles is a highly contagious illness. This means it's very easily spread to others. Measles is caused by a virus found in the nose and throat of an infected child or adult. When someone with measles coughs, sneezes or talks, infectious droplets spray into the air, where other people can breathe them in. The infectious droplets can hang in the air for about an hour. The infectious droplets may also land on a surface, where they can live and spread for several hours. You can get the measles virus by putting your fingers in your mouth or nose or rubbing your eyes after touching the infected surface. Measles is highly contagious from about four days before to four days after the rash appears. About 90% of people who haven't had measles or been vaccinated against measles will become infected when exposed to someone with the measles virus.