Measles is a serious contagious illness that's distinctive for the bright red spots that can spread over the entire body. One of the vaccines most young children receive helps keep them from getting measles.
Measles used to be a disease that killed many people — it's estimated that between the mid-nineteenth century and 2005, about 200 million people died from measles. Today about 85 percent of children worldwide are vaccinated against measles, so it's much less common than it once was. The word measles most likely comes from the Middle Dutch masel, or "blemish."