When it comes to measles, it’s a small world after all.
Our ability to hop aboard a plane and arrive a few hours later at “the happiest place on Earth,” coupled with low vaccination rates, has enabled a measles epidemic centered on Disneyland in California to spread thousands of miles from the theme park, a University of Pittsburgh Graduate School of Public Health epidemiologist explains.
According to the California Department of Public Health, at least 59 cases of measles have been linked to the Disneyland outbreak, which started in December. California’s Orange County – home to Disneyland – has one of the lowest vaccination rates in the U.S. due to unfounded concerns about vaccine safety.
“Measles is five times more infectious than the flu,” said Wilbert van Panhuis, M.D., Ph.D., assistant professor of epidemiology at Pitt Public Health and lead investigator for Project Tycho®, which tracks infectious diseases. “And you can contract it and then be contagious within a week. Infectious people can spread the disease for up to eight days, enabling the virus to travel far and wide, both into and out of Disneyland.”
According to the U.S. Centers for Disease Control and Prevention (CDC), measles is a respiratory disease that spreads through the air from coughing and sneezing. Due to the Disneyland outbreak, the CDC recently issued an alert notifying doctors nationwide to consider measles when diagnosing patients and to make sure their patients are up-to-date on their vaccines.
“The vaccine for measles is one of the safest, longest-used, most effective vaccines out there,” said Dr. van Panhuis. “It has been used all over the world to immunize millions of children and to stop measles epidemics. Project Tycho estimated that in the U.S. alone, the vaccine prevented 36 million cases of this deadly disease since it was introduced in the 1960’s.”
Measles vaccines are given at 1 and 6 years of age and work the best after both of these doses. So there are many infants and young children, and those with compromised immune systems, who cannot get the vaccine. Typically, those people are protected by “herd immunity” if enough people are immunized. Measles will not spread effectively if about 95 percent of the general population is vaccinated against it.
But in many Orange County school districts, the vaccination rate is far lower than 95 percent, and even drops as low as 50 percent in some schools. The safety net of herd immunity that could have protected young visitors to Disneyland was absent in Orange County, allowing this epidemic to take hold and persist.
So, Dr. van Panhuis explains, measles is able to spread into and from Disneyland because there is a better chance that an infected person will come in contact with someone else who isn’t vaccinated or doesn’t have full immunity. And then they’ll get sick and could spread it to someone else, perhaps all within a one-week stay at the theme park.
That means that Mickey Mouse himself – or the employee who dons the ears and hugs the kids – could be spreading the virus since employees who live in the area may be among the group of children who were never vaccinated.
“For the best experience in Disneyland or other parks,” Dr. van Panhuis says, “make sure your children are vaccinated before you go.”