The school district said the closures allowed for a deep cleaning after it reported on Thursday that 761 students and 63 school-level staff members were sick.

School is back in session today in Polk County after schools in the district closed their doors for a couple of days for cleaning.

Norovirus, often mislabeled as “stomach flu,” is a highly contagious virus causing vomiting and diarrhea. Unlike influenza, ...