Cases of measles linked to an exposure at Disneyland continue to spread, not just in California, but in several other states and in Mexico. The numbers of cases are climbing -- and so are the number of exposed people who might get sick -- and expose more people before they realize they are sick. Measles is extremely contagious; if someone has it, they will infect 90 percent of the people around them who aren't immunized.
It's scary, because measles can be dangerous. 1 in 20 people who get it will get pneumonia. 1 in 1,000 will get encephalitis, a brain inflammation that can lead to seizures and brain damage. 1 or 2 in 1,000 will die.