Researchers at the University of British Columbia have reported on their study that found traces of listeria in 40 fish product samples “tested before their expiry date.”

The study was conducted UBC food microbiologist Kevin Allen and published in the journal Food Microbiology. 

According to the Vancouver Sun:

The type of foods tested included lox, smoked tuna, candied salmon and fish jerky. The listeria was found in 20 per cent of the products tested, of those, five had the more virulent variety of listeria monocytogenes.   “Additional handling of ready-to-eat foods in stores, such as slicing, weighing, and packaging, may increase the potential for cross-contamination,” Allen said in a press release. “While listeria bacteria can be killed by high heat, most people eat these fish products without further cooking.”