Toronto has become food-obsessed in recent years - new restaurants, celebrity chefs and line-ups at every single brunch spot in town. But that obsession had a dark twist this summer, when the cronut burger took the city by storm.

For weeks leading up to the Canadian National Exhibition, the cronut burger, a hamburger patty between a Frankenbun made half from croissant, half from donut with bacon maple jam on top, was a cause celebre.

Its creators, Epic Burgers and Waffles, saw lineups that stretch almost outside the Food Building at the CNE from opening day onwards. The cronut burger was sold out almost daily.

Until four days into the annual summer carnival, when paramedics were brought into the fairground. At least 34 people reported feeling ill. Horrific stories of repeated vomiting, dizziness, blackouts and even temporary blindness surfaced. The fair opened on a Friday, and this was only Tuesday.

Rumours that the still super popular cronut burger was the source of the food poisoning began almost immediately.

Then it started to make sense. Epic Burgers and Waffles voluntarily shut down on Wednesday of that summer week.

Medical teams zeroed in on the unique burger, which appeared to be the link between all the illnesses. The teams took samples from the cronut burger and sent them to labs to be studied. The results would return in two to four days.

In the meantime, more and more people were turning up sick, and it increasingly looked as if cronut burgers were the culprit. By Thursday, 100 people reported food borne illness. By Friday, that number was 150.

Then, the results of the Board of Health’s investigation: staphylococcus aureus was present in lab tests performed on the burger. Officials determined a specific ingredient was contaminating consumers of the burger, and that was the maple bacon jam.

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The focus then moved to a small bakery on Dundas Street West called Le Dolci. As the supplier of the jam, the bakery closed for two weeks after the illnesses, but remains in business.

Troubles for CNE, however, continued, as more food vendors were shut down in following weeks. But by the end of its first week of the CNE, Toronto's cronut crisis was over.