The US Centers for Disease Control and Prevention (CDC) said there had been 19 cases from nine states – all those ill were hospitalized and one person died.
The Public Health Agency of Canada (PHAC) said there were 14 cases of Listeria monocytogenes in five provinces. All of them were hospitalized, and three people died, however it was not determined if Listeria contributed to the deaths.
Whole Genome Sequencing (WGS) on clinical isolates from ill people in Canada showed they were closely related genetically to Listeria isolates from ill people in the US.
Although the investigation began in September 2015, the source of the illnesses wasn't known until January this year. How salads became contamination has not been discovered.
Dole facility link
Packaged salads produced at the Dole processing facility in Springfield, Ohio and sold under various brand names were the likely source.
At the end of January, Dole recalled all salad mixes made at the plant and temporarily stopped production.
Items affected are identified with a product code beginning with the letter “A” in the upper right-hand corner of the package.
The products had a shelf-life of about 14 days, so it is unlikely that they are still in stores or consumers’ refrigerators, said the agencies.
Listeria specimens were collected from July 5, 2015 to January 31, 2016, said the CDC.
Ill people ranged in age from three to 83 and 74% were female. One person from Michigan died as a result of listeriosis.
Of 14 ill people asked about packaged salad, 13 (93%) ate a packaged salad. All of the nine ill people who specified the brand of packaged salad eaten reported various kinds of Dole brand packaged salad.
The Ohio Department of Agriculture collected a Dole brand Field Greens packaged salad from retail and isolated Listeria.
The Food and Drug Administration (FDA) confirmed Listeria monocytogenes in a packaged salad made at the Springfield, Ohio, facility.
PHAC said Laboratory results from the Canadian Food Inspection Agency (CFIA) confirmed a link between recalled packaged salad and the outbreak of listeriosis.
Five provinces were affected: Ontario (9), Quebec (2), New Brunswick (1), Prince Edward Island (1), and Newfoundland and Labrador (1).
Individuals became sick between May 2015 and February 2016. The majority (64%)were female, with an average age of 78 years.
Foods contaminated with Listeria may look, smell and taste normal. Unlike most bacteria, it can survive and sometimes grow on foods stored in the refrigerator.