The number of measles cases in California is rising. Seventy-nine people in the state are now known to be infected, 52 of them directly linked to Disney theme parks.
Measles can be transmitted much like the common cold. But you can catch it by breathing the air where an infected person has been as long as two hours ago.
"I would say it’s one of the most contagious diseases known to mankind," says Dean Blumberg, chief of pediatric infectious disease at UC Davis.
He says almost all recent outbreaks of measles in California have involved kids whose parents have opted out of the vaccine for personal beliefs.
He says even though more than 90 percent of kindergartners were vaccinated this school year, that's just a statewide average.
"Within communities such as school, you can get very high rates of personal belief exemption, and for measles, you need somewhere between 93 to 94 percent overall immunity to prevent further transmission, you can imagine if you have a school that has 10 percent or 20 percent personal belief exemptions, that really creates the conditions for which you can get continuing transmission," says Blumberg.
People who support personal belief exemptions from vaccinations question the safety of the shots, and say they have the right to make educated, voluntary choices.
Meanwhile, the Sacramento County Department of Health and Human Services confirmed this week that it has been testing two suspected cases of measles. Results in one case have come back negative.
The Sacramento Bee reports that another potential measles case in Sacramento County is being tested at the state lab.