"Here in Mariposa we have a lower uptake of vaccinations a higher rate of personal belief exceptions," said Dr. Eric Sergienko.
Dr. Sergienko with the county health department says they received an email from the state health department about the exposure a few days after a tournament in Turlock.
At least three high school students participated in the tournament on March 21, but Sergienko says a number of the students at the high school haven't had all or any of their measles shots.
"About 75 students at the high are not vaccinated. What we can do and what we're doing is to offer walk-in MMR vaccines," Dr. Sergienko said.
According to the Centers for Disease Control, the number of reported measles cases across the U.S. so far this year is more than all the cases reported in 2018.
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Heather Stovall brought in her daughter Charlie to get her second measles shot, not wanting to risk her getting sick.
"My friends who have kids enrolled in there who are actually my new neighbors, so yeah I found out about that, so I figured it's about time," she said.
She says another reason she had her daughter get the shot is because of the tourists coming to Yosemite.
Stephanie Raczkowski with the Mariposa County School District's says they've called families to let them know about the exposure, and have met with concerned students.
"I did meet with high schoolers who had not been vaccinated, they grew up thinking vaccines were unsafe," Raczkowski said. "They were surprised and wanted to get vaccinated."
Sergienko says they've determined the students at the tournament were all fully, or at least partially vaccinated, and while that lowers the risk, there's still a chance of transmission.
The school district and health officials are monitoring the students and following up.
They say they're just playing it safe, and none of the students have been diagnosed with measles at this time.
They do encourage anyone 18 and over who wants to be vaccinated to come to the health department.