More than 300 students and staff at the Delta Secondary School in Delta, B.C., have what's believed to be norovirus.
The Fraser Health Authority issued a warning to staff, students, and parents on Thursday, but says it's still working on confirming its suspicions through tests.
The authority says the school is undergoing enhanced cleaning and it's asking those who have symptoms of vomiting or diarrhea to stay home.
The gastrointestinal virus is highly contagious and people are usually infected through direct contact, such as sharing food or eating utensils, or touching contaminated surfaces or objects.
The virus usually passes after 24-to-48 hours in those who are otherwise healthy.
The authority is also recommending to those who are sick to stay at home for at least two days after their symptoms have stopped.
At the end of May, 20 per cent of the students in a Vernon school were also sick from a virus.