Chickenpox has taken hold of a school in North Carolina where many families claim religious exemption from vaccines.

Cases of chickenpox have been multiplying at the Asheville Waldorf School, which serves children from nursery school to sixth grade in Asheville, N.C. About a dozen infections grew to 28 at the beginning of the month. By Friday, there were 36, the Asheville Citizen-Times reported.

The outbreak ranks as the state’s worst since the chickenpox vaccine became available more than 20 years ago. Since then, the two-dose course has succeeded in limiting the contagious disease that once affected 90 percent of Americans.

The school is a symbol of the small but strong movement against the most effective means of preventing the spread of infectious diseases — like an island in the vast ocean of medical consensus. The percentage of children younger than 2 years who haven’t received any vaccinations has quadrupled since 2001, said the Center for Disease Control and Prevention.

Like the Disneyland measles outbreak in 2015, the flare-up demonstrates the consequences of a shadowy debate fueled by junk science and fomented by the same sort of Twitter bots and trolls that spread misinformation during the 2016 election. And it shows how a seemingly fringe view can gain currency in a place like Asheville, a year-round resort town nestled between the Blue Ridge and Smoky Mountains.

“The school follows immunization requirements put in place by the state board of education, but also recognizes that a parent’s decision to immunize their children happens before they enter school,” the school told Blue Ridge Public Radio.

Jennifer Mullendore, medical director of Buncombe County, N.C., was unambiguous: “We want to be clear: Vaccination is the best protection from chickenpox.”

“When we see high numbers of unimmunized children and adults, we know that an illness like chickenpox can spread easily throughout the community — into our playgrounds, grocery stores, and sports teams,” she said.

But not all parents seemed to grasp the gravity of the outbreak. Nor does everyone see the rationale behind vaccines, which some believe — contrary to scientific evidence — cause more severe health issues than they’re meant to cure. The claim of an autism risk, though it has been debunked, has remained a rallying cry of the anti-vaccine movement.

Chickenpox is serious, warns the CDC, “even life-threatening, especially in babies, adolescents, adults, pregnant women and people with weakened immune systems.”