The United States is on track to get hit with the biggest measles outbreak in more than seven years, the Centers for Disease Control and Prevention said today.
A series of outbreaks in nine states between January and April 25 has resulted in 64 measles cases -- the highest number reported over the same time period since 2001. Since last Friday, eight more cases have also been reported in Washington state.
Fourteen people have been hospitalized as a result of this year's measles outbreak. No deaths have been reported.
"I am concerned," said Anne Schuchat, director of the CDC's National Center for Immunization and Respiratory Diseases. "This is different than what we've been seeing the past few years."
Measles symptoms include spots, fever, rash, red eyes, cough and runny nose. Severe cases can lead to pneumonia and even death.
The reasons for the outbreak include more people who are choosing not to get vaccinated for both personal and religious reasons, Schuchat said. There's been a spike in the number of travelers bringing cases in from Israel and Europe.
"Many people don't think of traveling to Europe as a place where you can come down with an infectious disease," said Schuchat, who emphasized that travelers should stay updated on immunizations.
Of the 64 people who got measles, just one had received the full two doses of vaccine. All but 10 of those cases have been associated with the importation of measles from other countries, namely Switzerland and Israel.
The CDC revealed that in both countries, the measles outbreak occurred in communities where people tend not to get vaccinated.
About 96 percent of U.S. kindergarten-age children are vaccinated, but increasingly, there are pockets of people across the country who opt out of vaccines. Of the 59 measles cases among U.S. residents, 21 of the people were between 16 months and 19 years old -- and 14 of them claimed vaccination exemptions due to religious or personal beliefs.
"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.