Four cafeteria workers at York University’s Glendon College campus have tested positive for tuberculosis infections.

Toronto Public Health began testing food court staff this week after learning July 30 that one worker had fallen ill with the disease. As of Wednesday, three others had been found to be infected.

It is not known whether the staff contracted the disease from their co-worker. Tuberculosis infections can lie dormant in one’s system for years.

Tuberculosis is only contagious when one shows symptoms, which include a chronic cough, fever, night sweats and weight loss, said Julia Lechner of Toronto Public Health.

The three workers who tested positive this week are “not sick with TB. They just have the germ in their body from an exposure at some time in their life,” she said.

The first worker to be diagnosed is mildly contagious. She fell ill in mid-June and was diagnosed in late July, when her local health unit contacted Toronto Public Health and she took leave from the cafeteria.

Tuberculosis is spread when someone sick with the disease coughs or sneezes. However, the risk to students is very low, even if they ate at the cafeteria daily, said Dr. Monica Hau of Toronto Public Health.

“In tuberculosis you really need close and prolonged contact to be infected,” she said. “A brief encounter would not, in this case, require any screening.”

The health board is testing 20 food court employees, beginning with skin tests this week. It will test them again in eight weeks, to ensure enough time has passed for the slow-moving disease to appear.

Those who tested positive are now taking antibiotics to treat the infections. They will not take leave from work as they are not contagious.

Aramark Canada, which runs the food court, and York University both said they are aware of the situation and actively co-operating with Toronto Public Health.

All four of the food court workers were born outside of Canada. About a third of the world’s population is infected with tuberculosis, according to the World Health Organization.

Toronto Public Health deals with 300 tuberculosis cases a year. The disease can be lethal, but is highly curable due to widespread access to antibiotics.