Nine U.S. states have reported measles cases this year, the highest incidence since 2001. Of the 64 cases, 63 occurred in people without vaccinations.

From January 1 through April 25, 2008, CDC received a total of 64 reports of confirmed measles cases in nine states — the highest number for the same time period since 2001. In four of the states — Arizona, New York, Michigan, and Wisconsin — outbreaks (3 or more cases linked in time or place) are ongoing. Outbreaks may occur when measles cases are imported into the U.S. Ten of the recent case-patients (5 US residents and 5 visitors to the U.S.) acquired measles abroad, and the remaining cases are considered linked to the imported cases.

http://www.cdc.gov/Features/MeaslesUpdate/