An outbreak of norovirus has been reported at an elementary school in Thornhill.

Thornhill Woods Public School Principal Lynne Cohen sent a memo to parents, on Monday, advising them of the outbreak and asking them to keep any children with the highly-infectious virus at home until they are symptom free for at least 48 hours.

Some of the symptoms of norovirus, also known as Norwalk, include diarrhea, vomiting, nausea, cramps, muscle aches, fatigue and fever. Symptoms usually dissipate after 24 to 48 hours.

“We are working alongside public health and various school board departments to clean, sanitize and disinfect the school. Our caretakers worked all weekend to complete the process for Monday,” Cohen wrote. “Of paramount importance, is the requirement that students who are ill do not return to school until they are free of symptoms for 48 hours. This is essential so that we do not undo the work done over the weekend to disinfect and sanitize the building.”

Norovirus is a highly contagious virus that causes inflammation of the stomach and intestines.

Symptoms usually occur 12 hours after exposure to the virus but can take as long as 24 to 48 hours to manifest.

In her letter, Cohen said that she is hopeful that the outbreak has already been addressed; however she said it is important the virus is not brought back to the school community by students still dealing with it.

“We are helpful that with the help and support of public health our school board and all the work done this weekend that we should be over the outbreak provided that the virus is not reintroduced this week,” she wrote.