Measles is a highly contagious disease caused by a virus. Measles starts with a fever. Soon after, it causes a cough, runny nose, and red eyes. Then a rash of tiny, red spots breaks out. It starts at the head and spreads to the rest of the body. Measles can be serious for young children. It can lead to pneumonia, encephalitis (swelling of the brain), and death.
Measles spreads through the air when an infected person coughs or sneezes. It is so contagious that if one person has it, 90% of the people around him or her will also become infected if they are not protected.
People in the United States still get measles, but it's not very common. That's because most people in this country are protected against measles through vaccination. However, since measles is still common in parts of Europe, Asia, the Pacific, and Africa, measles is brought into the United States by people who get infected while they are abroad.