The Centers for Disease Control and Prevention (CDC) reported on Thursday that the Listeria outbreak, which started in May 2015 from eating salads by Dole Processing Facility in Ohio, is now over. This multistate outbreak affected people from nine different states of US and Canada. According to CDC, Listeriosis claimed one life from Michigan before being allegedly eradicated while sent 19 people to hospitals across the States. In Canada, 14 people got infected and three of them died. However, the deaths in Canada have not been directly linked with Listeria, health officials claimed.

‘Dole’ Salad Listeria Outbreak Is Over

The rare and deadly Listeriosis infection is caused by a bacterium strain known as Listeria monocytogenes, usually found in soil, water and some animals.

A collaborative investigation by FDA and CDC was launched into different packaged salads produced at the Dole Processing Facility. The bacteria-carrying salads were sold under these brand names: Fresh Selections, Simple Truth, Marketside, The Little Salad Bar and President’s Choice, and identified as the original source of infection. The manufacturing code of all the products started with the letter ‘A’.

On 22nd January, 2016, CDC confirmed the source of infection in a statement, “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.”

Investigative Methods

The authorities employed Whole Genome Sequencing technique (WGS) along with Pulsed-Field Gel Electrophoresis (PFGE) to investigate the strain of Listeria isolated from the infected people. The genome sequences of the isolates obtained from all 19 patients showed close structure similarities with each other, proving they were from the same source. PFGE technique was also used to identify Listeriosis infection in February 2015, which was linked to caramel apples.

On January 21, 2016, Dole reported to the CDC about ceasing production at their processing unit in Springfield, Ohio. Dole removed all of their packaged salads from the U.S. market. A food recall warning was also launched by the Canadian Food Inspection Agency (CFIA) against Dole on the 22nd of January, 2016. People from the five eastern provinces of Canada also reported contracting the same Listeria strain infection, as same types of salads from the Dole’s facility were exported to Canada too during May 2015 and early January 2016. The genome sequences of the bacteria found in Canada shared structural similarities with the strain found in the U.S., as reported by the Public Health Agency of Canada.

Dole took the matter seriously and shut down production at their plant. Later, on January 27, 2016, Dole recalled all of their salads from the market to avoid further damage. CDC has also assured that the infection is contained, saying any salads still available in the market would have expired by now, as their shelf life is only 14 days. Meanwhile, on January 28, 2016, FDA completed its final analysis and confirmed the presence of ‘Listeria monocytogenes’ in packaged salads produced at the Springfield, Ohio, facility.

CDC And FDA Investigation

The results of the CDC and FDA investigation suggested close structural similarities in all the strains found in the infected individuals. The victims of Listeriosis belonged to different age groups ranging from 3 to 83 years old in the U.S. The FDA started the investigation by taking complete dietary history recall of the patients. They were asked about the types of foods eaten. 14 out of the 19 patients confirmed eating a packed salad, nine people confirmed brand names of the salad produced by Dole. The Department of Agriculture, Ohio, carried out a routine laboratory checkup on the Dole branded salads, obtained from a retail location, and found Listeria monocytogenes.

Despite this, the CDC and FDA have suspiciously remained silent on further progress in the Dole investigation. The FDA has not revealed any further details on the salad plant inspection in Springfield since January 29th. FDA even denied a request from the Food Safety News for the Form 483 on the Dole facility inspection and stated FSN would have to file a Freedom of Information Act request.

Meanwhile, a woman named Constance Georgostathis from Ohio, whose mother Angeliki “Kiki” Christofield suffered from a coma and months of recovery after eating a Listeria contaminated salad, is filing a lawsuit against Dole Food Co. Constance is seeking unspecified damages for her mother from the federal court.

The Public Health Agency of Canada (PHAC) stated on March 17, 2016, “The outbreak investigation coordinating committee has been deactivated and the investigation is coming to a close.”

Listeriosis Sources And Symptoms

The US Food Safety Department and CDC stated that Listeria bacterium can grow even in the cold temperatures of a refrigerator. As Listeria is only killed by cooking and pasteurization, the salads at Dole’s facility possibly carried the bacterium from soil, which further multiplied in the salads upon refrigeration.

CDC reported that people with weakened immune system are more prone to the infection including pregnant women and elderly people. Headache, fever, stiff neck, convulsions, loss of balance and muscle aches are major symptoms of the infection. Listeriosis in pregnant women can lead to miscarriage, stillbirth, premature delivery, or life-threatening infection of the newborn.