Twelve people infected with the outbreak strain of Listeria monocytogenes have been reported from six states since July 5, 2015, said the US Centers for Disease Control and Prevention (CDC).
The Public Health Agency of Canada (PHAC) said there are seven cases in five provinces reported since September last year.
Finding illness source
Although the investigation began in September 2015, the source of the illnesses wasn't known until January 2016 when the laboratory result from the packaged salad collected in Ohio linked the illnesses to the Dole processing facility in Springfield, Ohio, said the CDC.
It added all 12 people were hospitalized, including one person from Michigan who died as a result of listeriosis. One illness was reported in a pregnant woman.
Five of the five ill people asked about packaged salad reported eating it in the month before becoming ill. Two of two ill people who specified a brand of packaged salad reported eating various varieties of Dole branded ones.
Brands of packaged salads include Dole, Fresh Selections, Simple Truth, Marketside, The Little Salad Bar, and President's Choice Organics.
These packaged salads can be identified by the letter "A" at the beginning of the manufacturing code found on the package
The Ohio Department of Agriculture collected a Dole brand Field Greens packaged salad from retail and isolated Listeria. Laboratory tests showed that the Listeria isolate from the packaged salad was highly related genetically to isolates from ill people.
At this time, there is no evidence to suggest that packaged salads produced at other Dole processing facilities in the US are linked to illness, said the CDC.
Ill people are from: Indiana (1), Massachusetts (1), Michigan (4), New Jersey (1), New York (4), and Pennsylvania (1). Dates of Listeria specimen collection range from July 5 to December 23.
Whole genome sequencing (WGS) on clinical isolates from all ill people showed that the isolates are highly related genetically to one another, said the US Food and Drug Administration (FDA).
Dole withdrawal and Canada investigation
Dole said it is withdrawing all Dole-branded and private label packaged salads processed at the factory.
The firm added it has temporarily suspended operations at the site.
A list of affected states and provinces can be found here.
Other Dole products, including fresh fruit, fresh vegetables and packaged salads from Dole’s other processing facilities (with product codes beginning with “B” or “N”), are not part of the withdrawal.
The products may have been repackaged or transformed into various in-store produced products, such as in-store made salads.
PHAC said individuals became sick between September 2015 and early January 2016 and some reported eating packaged salads.
The majority of Canadians cases (71%) are female, with an average age of 81 years.
All cases have been hospitalized, and one person has died, however it has not been determined if Listeria contributed to the cause of death.
Infections have been reported in Ontario (3), Quebec (1), New Brunswick (1), Prince Edward Island (1), and Newfoundland and Labrador (1).