Measles is a highly contagious viral disease that causes fever, coughing, and a distinctive red rash that spreads across the body. Before vaccines became widely available in the 1960s, measles infected millions of children every year, causing serious complications and even death in some cases. The disease spreads through the air when an infected person coughs or sneezes, and it's so contagious that if one person has it, up to 90% of nearby people who aren't immune will catch it too.

The measles vaccine, usually given as part of the MMR shot (measles, mumps, and rubella), has proven remarkably effective. In countries where most children receive the vaccine, measles has become rare. The vaccine works by training your immune system to recognize and fight the virus without you actually getting sick.

When doctors or public health officials talk about measles outbreaks, they mean situations where the disease starts spreading in a community, usually among unvaccinated people. The rash usually starts on the face and moves down the body, and sick children often feel miserable for about a week. While most children recover fully, measles can sometimes cause serious complications like pneumonia or brain inflammation, which is why vaccination programs have worked so hard to eliminate this disease.