LOS ANGELES, MAY 2: The US is on track to report its highest incidence of measles cases since 2001, health officials said Thursday, exacerbated by a rise in outbreaks worldwide and clusters of people who are opting out of the vaccine because of religious beliefs or fears of a purported link between the shot and autism.

As of April 25, there were 64 reported cases of measles nationwide this year, including 12 in San Diego. One in five cases required hospitalisation, said Anne Schuchat, director of the National Center for Immunization and Respiratory Diseases at the US Centers for Disease Control and Prevention. There were about 30 cases of measles in 2007.

Before the advent of federally funded vaccine programs in the past decade, outbreaks were typically among low-income children who lacked access to vaccinations.

“Now, I think we’re seeing a different trend with communities or pockets of under-immunized children that are more linked to (vaccine exemption),” Schuchat said.

Measles is a highly contagious disease that can cause a rash, high fever, cough, runny nose and red watery eyes. It can also cause diarrhea, ear infections, pneumonia, brain injury, seizures and death.

Before the measles vaccine was introduced in 1963, there were up to 4 million reported cases and up to 500 deaths every year in the United States. But vaccination programs subsequently were so successful that public health officials declared widespread transmission of the disease eliminated in 2000. The recent outbreak that infected a dozen children in San Diego underscored the concern of public health officials. A 7-year-old unvaccinated boy visited Switzerland and then brought the disease to his school in January.

Nearly 10 per cent of the students at the San Diego Cooperative Charter School had received personal belief exemptions from vaccinations.