From the New York Times:
Measles cases quadrupled in the United States last year, but outbreaks are still rare compared with those in Europe, the United States Centers for Disease Control and Prevention said Thursday. There were 222 cases of measles reported in the United States, a third of which required hospitalization, the agency said. Most of those 17 outbreaks are known to have begun in foreign visitors or in Americans returning from abroad — usually from Europe. But the virus then often spread to children whose parents did not vaccinate them. Vaccination resistance is concentrated in certain communities, making children there more vulnerable. By contrast, there were 37,000 measles cases last year in Europe, where resistance to vaccination is more common.