Most commonly characterized by a rash that begins on the face and spreads throughout the body, measles is a serious condition that can lead to brain infection and death. Though historically a devastating disease, it has experienced steep decline ever since the early 1960s, when the measles vaccine was first developed. Today it is administered to most children in the United States via the MMR vaccination.
In 2011, 222 measles cases were reported in the United States, the highest level in 15 years. Previous to that, only about 50 cases of measles were reported annually in the U.S., most of which were contracted outside of the country.
This thin-section transmission electron micrograph (TEM) shows a single virus particle, or virion, of measles virus.