Teachers and students at a private Niagara on the Lake school are being tested for tuberculosis after a student was diagnosed with an active case of the infectious disease.
The 18 year old student from China who attends the Royal Elite International Academy, tested positive in February.
The Toronto Star is reporting that at least eight students and four teachers have since tested positive for TB.
Niagara's Associate Medical Officer of Health will not confirm the numbers citing privacy rules.
Doctor Mustafa Hirji also notes that a positive test does not mean the patient has active or latent TB, but it does mean chest X-rays have to be done to further confirm the diagnosis.
The doctor adds about 95 percent of people with latent TB never develop the disease and are not infectious.