The airborne, highly infectious virus is best stopped by getting vaccinated, officials said.
Robert Gauthier/Los Angeles Times / MCT
The new cases bring the total number of confirmed measles cases in the latest outbreak to 53, health officials said.
The outbreak also prompted one Southern California school to send home its students who have not been vaccinated, ABC 7 reported. A student at Huntington Beach High School attended class for three days this month while sick with measles. As a result, 24 unvaccinated classmates have been asked to stay home while parents keep an eye out for symptoms.
About 91% of California children have received the measles vaccine, according to the state department of health's most recent survey. Vaccines are required to attend public school, though parents may file for an exemption for personal or religious reasons.
Health officials believe one person already sick with the highly contagious virus went to Disneyland or the neighboring California Adventure between Dec. 15 and 20, infecting visitors.
Most of the confirmed cases are in California, although there are three in other states and Mexico, the Los Angeles Times reported. Most spent time in the parks in December, though a few may have caught the illness from others who visited.
San Diego health officials said Monday they were investigating three new “probable cases of measles.”
The three people visited Disneyland Dec. 18 and had not been vaccinated for measles, the County of San Diego Health and Human Services Agency said. If they test positive for the virus, it would bring the total number of confirmed cases in the county from 10 to 13.
Lab tests are expected to be completed this week. The County of San Diego Health and Human Services Agency also released a list of places where the public may have been exposed.
In Colorado, health officials said a measles patient was treated at Penrose Hospital in Colorado Springs and may have exposed more people to the virus. Another woman traveled from Orange County to Washington via Sea-Tac Airport, Washington health officials said. She also spent time in other public places, including shops and an emergency room, before flying home to Orange County.
The patients range in age from infants to adults, officials said. Some were partially vaccinated and at least two were too young to have been administered the vaccine, according to the AP.
Measles has been essentially eliminated in the U.S. since 2000, but in Western Europe, large outbreaks have occurred amid declining vaccination rates.
“Measles vaccination is important because before the introduction of measles vaccine in the United States in 1963, there were approximately 500,000 cases and 500 deaths a year,” said Carlos Villatoro of the California Department of Public Health, adding that 90% to 95% of the population must be immune to measles to sustain the virus' elimination.
The virus travels through the air, Villatoro said, and where it can linger for up to two hours and travel long distances on air currents. In one measles outbreak, the virus spread from one person in a sports arena to another sitting 100 feet away, Villatoro said.
Patients typically develop a rash two weeks after being exposed to the virus. They are contagious four days before the rash develops and four days after.
Before the rash develops, symptoms include runny nose, high fever, red eyes and a cough.
Almost all U.S. measles cases can be traced to a traveler who spent time in countries where measles is prevalent, officials said. With Disneyland's worldwide popularity, officials said that's probably what happened this time as well.
“We have not identified the source case for this outbreak, but it is likely to have been an international visitor,” Villatoro said.