WASHINGTON (Reuters) - The biggest U.S. outbreak of measles since 2001 is unfolding in 10 states, with at least 72 people ranging from infants to the elderly becoming ill -- most of them unvaccinated, U.S. health officials said on Thursday.

The U.S. Centers for Disease Control and Prevention said none of those who caught the highly contagious viral illness has died, but at least 14 people have been hospitalized, most with pneumonia triggered by measles.

There were 116 cases in 2001, and the last major U.S. outbreak occurred from 1989 to 1991, when 55,000 people got measles and 123 died.

Anne Schuchat, who heads the CDC’s National Center for Immunization and Respiratory Diseases, said she expects “many more cases this year than we had in 2001 based on what’s going on today.”

Public health officials have been stressing the importance of immunizing children in the face of increasingly vocal groups who object to vaccines for religious reasons or because they think the shots may cause autism or other problems.

CDC officials said overwhelming scientific evidence points to the safety of the combined measles-mumps-rubella, or MMR, shot and other childhood vaccines.

“We are concerned ... about the population of people who are choosing not to be vaccinated, and whether we may be on the verge of facing larger-scale outbreaks in the United States,” said Jane Seward of the CDC’s division of viral diseases.

The CDC said most of the measles cases can be traced to 10 people who picked up the disease overseas and then traveled back to the United States, where others became infected. The ages of those sickened ranged from 5 months to 71 years.

GLOBAL PROBLEM

“These cases and outbreaks resulted primarily from failure to vaccinate, many because of personal or religious belief exemption,” the agency said in a statement.

The CDC said 64 cases were reported from January 1 through April 25 in Arizona, California, Hawaii, Illinois, Michigan, New York, Pennsylvania, Virginia and Wisconsin.

Eight more confirmed cases -- all involving unvaccinated children in one family who had attended a church gathering in the Seattle area -- have been reported since then in Washington state, the state department of health said on Thursday.

Those spreading measles were infected in Switzerland and Israel, both of which have larger outbreaks, as well as in India, Belgium, Italy and likely China and Japan, the CDC said.

“Transmission has occurred in community and health care settings, including homes, child care centers, schools, hospitals, emergency rooms and physicians’ offices,” it said.

The disease causes fever, cough, redness and irritation of the eyes and a rash. Serious complications include encephalitis and pneumonia that can be fatal. Measles remains a leading cause of death among children in poor countries, killing about 250,000 people a year globally.

Before a vaccine was introduced in 1963, more than half a million people got measles in the United States and 500 died annually. Thanks to the vaccination program, measles is no longer endemic in the United States, and ongoing transmission of the virus was declared eliminated in 2000.

The annual number of cases since then generally has been in the dozens and caused by someone infected in another country.