The Public Health Agency of Canada is investigating an outbreak of listeriosis in five eastern provinces, which has resulted in the hospitalization of seven people, one of whom has died.

It's linked to similar outbreak in the United States, which killed one of the 12 people hospitalized, and has been traced to packaged salads produced at the Dole processing facility in Springfield, Ohio, the Centers for Disease Control and Prevention (CDC) announced on Friday.

tp-listeria-culture-cbc

Listeriosis is a rare but serious disease caused by listeria bacteria, which is often found in food. (CBC)

Dole has stopped all production at the facility and is withdrawing from the market all packaged salads produced there, which can be identified by the letter A at the beginning of the manufacturing code on the package, CDC said in a statement.

The salads were being sold under various brand names including Dole, Fresh Selections, Simple Truth, Marketside, The Little Salad Bar, and President's Choice, it said.

PHAC officials have now confirmed the outbreak currently under investigation in Canada is related to the U.S. outbreak.

Spokesperson Rebecca Gilman said in an email, "based on the epidemiological investigation we believe that these two outbreaks are linked. We are awaiting final laboratory confirmation of the genetic fingerprint of the outbreak strain." 

Gilman said a public warning to consumers not to consume the products will be issued.

Earlier this week, the federal agency said in a statement that the source of the outbreak in Canada has not yet been confirmed, but prepackaged leafy greens, salad blends and salad kits are food items being investigated.

'Risk to Canadians is low'

Ontario has had three cases of the "rare but serious disease," while New Brunswick, Quebec, Prince Edward Island and Newfoundland and Labrador have all reported one case each.

All seven people became sick between September and early January and have been hospitalized.

"One person has died, however it has not been determined if listeria contributed to the cause of death," the PHAC statement said.

The average age of those affected is 81, it said.

'In serious cases, listeriosis can lead to brain infection and even death.' - Public Health Agency of Canada

"At this time, the risk to Canadians is low."

In the United States, 12 cases have been reported in six states since July 5, CDC said in a statement.

Michigan and New York have each had four cases, while Indiana, Massachusetts, New Jersey and Pennsylvania have each had one. Those affected have been between the ages of three and 83, with a median age of 66.

All 12 people were hospitalized and one person from Michigan died as a result of listeriosis, according to CDC.

"Epidemiologic and laboratory evidence available to date indicate that packaged salads produced at the Dole processing facility in Springfield, Ohio, and sold under various brand names are the likely source of this outbreak," the statement said.

CDC is recommending that consumers do not eat packaged salads produced at Dole's Springfield facility, that restaurants do not serve the salads, and that retailers do not sell them.

"At this time, there is no evidence to suggest that packaged salads produced at other Dole processing facilities in the United States are linked to illness," it said.

Some people at higher risk

Listeriosis can cause vomiting, nausea, cramps, muscle aches, diarrhea, constipation, severe headache, a stiff neck and persistent fever, confusion and loss of balance.

"In serious cases, listeriosis can lead to brain infection and even death," according to the Public Health Agency of Canada website.

Jennifer Russell

Dr. Jennifer Russell, New Brunswick's acting chief medical officer of health, says unlike most bacteria, listeria can survive and sometimes grow on foods being stored in the refrigerator, but can be killed by cooking food properly. (Shane Fowler/CBC)

The elderly and those with weakened immune systems are at higher risk of more severe illness, Dr. Jennifer Russell, New Brunswick's acting chief medical officer of health said in a statement on Friday.

In pregnant women, listeriosis can lead to premature delivery, infection of the newborn baby or miscarriage.

Listeriosis is caused by a type of bacteria called listeria, which is often found in food.

Food that's contaminated with listeria may not look or smell spoiled, but it can still make people sick.

And unlike most bacteria, listeria can survive and sometimes grow on foods being stored in the refrigerator, said Russell.

​High-risk foods include:

  • Uncooked meat and vegetables including pre-packaged leafy greens.
  • Unpasteurized (raw) milk and cheeses and other food made from unpasteurized milk.
  • Ready-to-eat meats such as hot dogs, pâté and deli meats.
  • Refrigerated smoked seafood and fish.

Listeriosis can be avoided by cooking food properly and by following safe food handling practices, such as:

  • Thoroughly cleaning fruits and vegetables under cool running water.
  • Thoroughly cleaning and sanitizing all surfaces used for food preparation.
  • Thoroughly cooking all foods.
  • Refrigerating or freezing prepared food and leftovers within two hours.
  • Keeping leftovers for a maximum of four days.
  • Reheating leftovers to an internal temperature of 74 C.

The mild form of foodborne listeriosis usually begins about three days after eating heavily contaminated food, while the incubation period for the more serious form of the disease could be up to 70 days after exposure.

Listeriosis is treated with antibiotics.