ASHEVILLE, N.C. — Health officials say 28 private school students in North Carolina now have chickenpox in an outbreak that began last week.

The number of children infected grew from 13 the week before, the Buncombe County Health and Human Services Department announced Monday.

In a statement, the Asheville Waldorf School said it has provided information about the outbreak to the health department.

Buncombe County Medical Director Dr. Jennifer Mullendore said students who can’t provide proof of vaccination against chickenpox have been quarantined for 21 days.

The private school serves students from nursery school age to Grade 6. One of the infected children attends a different school.