LOS ANGELES (Reuters) - A measles outbreak that has sickened at least 113 people in California after surfacing at a Disneyland resort involves a virus strain that also caused an outbreak in the Philippines, but it is too early to tell if the two waves of illness are related, health officials said.

The measles outbreak that began in late December renewed a debate about some parents' decisions to not vaccinate their children over fears about potential side effects of vaccines, which were largely fueled by now-debunked research suggesting the inoculations have a link to autism.

California Department of Public Health researchers, in a report to federal officials released on Friday, said the source of the illness that sickened visitors at the Disney theme park in December has not been identified.

"Specimens from 30 California patients were genotyped; all were measles genotype B3, which has caused a large outbreak recently in the Philippines, but has also been detected in at least 14 countries and at least six U.S. states in the last six months," the report stated.

The Disneyland resort, located in Anaheim in Southern California, receives millions of visitors a year with many of them coming from overseas.

The report posted on the website of the federal Centers for Disease Control and Prevention said the outbreak illustrates the need for high measles vaccine rates in the United States.

On Tuesday, California public health officials urged residents to vaccinate themselves and their children before traveling internationally over spring school break.

(Reporting by Alex Dobuzinskis; Editing by Lisa Lambert)