Measles infections in the U.S. have soared to the highest level in two decades, according to the CDC. At least 288 cases have been recorded in 18 states and New York City as of May 23. That is the most cases for this time of the year in the U.S. since 1994, when 764 cases were logged by May, officials said. Contributing to the rise are measles infections imported by unvaccinated travelers who brought the highly contagious virus home to vulnerable communities. About 97 percent of cases reported so far have originated from other countries.