“We wanted to make our entire district aware of this situation to ensure you are alert to the signs and symptoms and to recommend you consult your family health-care provider should you or your child(ren) present symptoms,” Todd Stitzel, director of human resources of Radner Township School District, wrote to parents, according to the Philadelphia Inquirer.

Scabies can spread rapidly under crowded conditions where close body contact is frequent. It’s caused by an infestation of the skin by the human itch mite, which burrows into the upper layer of the skin where it lives and lays its eggs, producing an intense itching and pimple-like skin rash, according to the Centers for Disease Control and Prevention (CDC). But in some cases, a person may not present symptoms, or it can take four to eight weeks to develop after they are infested. However, it is possible to still spread scabies despite not having any symptoms.

Products used to treat scabies are only available with a prescription, but bedding, clothing and towels used by an infested person should be decontaminated by washing in hot water and drying in a hot dryer. Scabies mites typically do not survive more than two to three days away from human skin.

A spokesperson for the district told the Inquirer that custodians were sanitizing the schools’ restrooms, wiping down desks, door handles and mopping nightly.