"I am concerned that those communities may be growing," Schuchat said. "I think we have some circumstances today that will make this continue to be challenging to us."
Schuchat said the additional outbreak of measles reported at a large church conference in Washington state happened among a group of people who do not believe in the vaccination.
The measles news comes after a report this week from the CDC, suggesting that fewer children in the United States are getting the immunizations they need.
More than one in four children are not in compliance with official vaccination recommendations because of missed doses of vaccines or vaccine lapses, CDC researchers found.
"Babies too young to be immunized really depend on other people being immunized -- the older siblings and family members and the community," Schuchat said.
Measles may also be picked up in doctors' offices, where health care professionals and parents alike may be less familiar with the disease than were previous generations, the CDC said.
People from five months old to 71 are among those who have contracted measles. Twenty-two of the reported cases were in New York City. Another 15 were in Arizona and 12 occurred in California.
In 2006, health officials saw just 55 cases of measles all year, compared with the 64 they've already seen in 2008.
The last major measles outbreak happened in the early 1990s. That resulted in 50,000 cases of measles, more than 11,000 hospitalizations and more than 120 deaths.
ABC News' Brian Hartman and Audrey Grayson contributed to this report.
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