A person infected with the measles visited Disneyland last week, prompting health officials to warn that hundreds of others may have been exposed to the disease.

Medical Ethicist Arthur Caplan joined Boston Public Radio Friday to explain exactly why this has health officials on high alert.

"It's one of the most contagious diseases there is," he said. "Highly infectious, way way more than things we hear about like Ebola, even more infectious than the flu. It lingers in the air, especially if you're in a contained area. ... I think it's morally selfish and morally outrageous that you would take an unvaccinated kid or a symptomatic kid anywhere, much less to a park like this."

Disneyland has been the site of a major measles outbreak before: A 2014 outbreak prompted California to strengthen its law requiring vaccinations after about 150 cases were confirmed across seven other states, according to the CDC.

Arthur Caplan is the Drs. William F and Virginia Connolly Mitty Chair, and director of the Division of Medical Ethics at NYU Langone Medical Center. He's also the co-host of the everyday ethics podcast.