More than 50 cases of measles have now been linked to the outbreak that started spreading at Disney theme parks in Southern California right before Christmas. And health officials report an increase in cases among people who did not visit the parks, indicating that the illness is now spreading to others exposed in their communities.
The latest figures from the California Department of Public Health identify 51 confirmed cases of measles. The majority -- at least 41 cases -- are in California. Most of the patients had not been vaccinated.
Health officials in Utah confirmed Monday that a third person in that state has been diagnosed: an unvaccinated child who had contact with two siblings who were infected at one of the parks.
Cases have also been reported in Washington state, Colorado and Mexico among people who visited Disneyland or Disney California Adventure Park in late December and got sick after they got home.
In Orange County, California, where at least 16 people have gotten sick, officials say the 6 most recent patients were not at Disney and did not have known contact to any of the confirmed Disney visitors. That worrisome development "indicates exposure to measles is more widespread throughout the county," the agency said in a statement. It went on to say officials expect "the measles outbreak will continue to spread."
Measles is highly contagious and can spread through a sneeze or cough before a person even knows they have it. The virus can remain airborne and live on surfaces for a period of time, making transmission harder to trace.
The Centers for Disease Control and Prevention says symptoms of measles typically appear one to two weeks after exposure and may include runny nose, watery eyes, cough and a high fever. Then a telltale raised, red rash starts to spread on the face and down the body.
Most patients recover, but some can develop serious complications or even die. The CDC says one out of every 20 children with measles will get pneumonia, and one out of 1,000 will develop encephalitis, or swelling of the brain, which can lead to convulsions and leave the child deaf or with mental retardation.
Before the vaccine became available in 1963, the CDC says 400 to 500 Americans died of measles every year and 4,000 suffered encephalitis from it.
Vaccination efforts were successful enough that measles was officially declared eliminated in the U.S. in 2000. But cases still occasionally emerge, mostly among unvaccinated people who contracted it overseas in countries where the illness is more common. Experts say a crowded place full of international visitors like Disneyland would be an easy place for it to spread.
"This outbreak is a reminder that measles is just a plane ride away from the United States," the California Department of Public Health noted.
Nationwide, the measles vaccination rate is over 90 percent, but some communities -- including Orange County and other parts of California -- have seen an increase in parents refusing vaccination for their children.
"Getting everybody vaccinated is so important because trying to contain these infections can really be difficult," Dr. Matt Zahn, medical director of Orange County Health Care Agency, told CBS News last week. "The vaccines work, the vaccines are safe, there are significant diseases out there that you can protect your children from."
California had its worst measles outbreak in decades last year, and many cases were linked to families who opted out of having their children vaccinated. Overall the U.S. had 644 confirmed cases of measles in 2014, the most in 20 years.