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According to Centers for Disease Control and Prevention (CDC) researchers analyzing two Listeria outbreaks linked packaged salads, routine surveillance is key to prevention strategies.
Between 2015 and 2024, there were eight Listeria outbreaks linked to packaged salads. Reports indicate that four of those outbreaks had a confirmed link to packaged salads. The other four were suspected. As a result, 240 packaged salad products were recalled “because of potential contamination with L. monocytogenes.”
Leafy greens are especially vulnerable to Listeria contamination because the germ not only survives well under refrigerated conditions, but certain varieties like romaine and iceberg can internalize it. Packaged salads also have inherent risk factors, despite many being “pre-washed,” in that there are more opportunities for touch points in the supply chain. Additional equipment and processing are necessary for packaged salads as opposed to picked varieties.
Listeria outbreaks linked to packaged salads can be difficult to investigate. The study cites some common factors, including relatively low case numbers, long incubation periods, older patients may have poor food recall or become too sick to provide food history. For this reason, Listeria outbreaks often take longer to solve than outbreaks caused by other common pathogens. Environmental sampling, rather than patient epidemiology, are major factors in identifying the food vehicle. Paired with the complication that many packaged salad products are processed by the same facilities, increasing the changes of cross-contamination.
Combine this with low-level contamination causing sporadic infections, protective biofilms preventing effective sanitation, and that sampling efforts typically only occur at the farm level once an outbreak is identified.
This study, published in the CDC’s Morbidity and Mortality Weekly Report as “Two Concurrent Outbreaks of Listeria monocytogenes Infections Linked to Packaged Salads, United States, 2014-2022,” involved two genetically unrelated outbreak strains. The sources were completely separate.
Combined, these outbreaks resulted in 30 illnesses, 27 hospitalizations, and four deaths over the course of eight years.
What makes these outbreaks different?
Both were investigated over an extended period of time.
One outbreak, named “Outbreak A” was investigated three different times with illnesses occurring over an eight-year span. “Outbreak B” spanned five years.
The first outbreak, Outbreak A, was initially detected in 2019 through PulseNet. A national foodborne illness database. Five cases across five states were initially detected. The outbreak strain reappeared in the PulseNet database in 2020. Then again in 2021.
Next came Outbreak B. A cluster of ten cases related to water-sediment samples from the Salinas Valley of California joined the PulseNet database. At least ten people across eight states were involved in this outbreak.
In this case, known environmental factors caused the two Listeria outbreaks linked to packaged salads. A 2014 US Department of Agriculture (USDA) study looking at the California watersheds connected to a major leafy green production region had serious Listeria contamination.
Nearly half (43%) of the environmental samples collected were positive for Listeria monocytogenes.
That is significant!
Water sampling from the Salinas Valley leafy green production region eventually broke the case. Or rather, cases. Even with that knowledge, narrowing a specific supplying farm was difficult.
Samples taken from irrigation water matched samples from outbreak patients. This was traced back to the originating farms.
With Listeria outbreaks so difficult to identify a source, and environmental sources being a common vector, wouldn’t it make sense for regulatory agencies to amp up surveillance sampling activities as a preventative measure.
In theory (and in practice), of course it would.
However, manpower, resources, and other factors may limit these surveillance activities at an effective level.
Could these regulatory agencies mandate farms to self-test? Require the necessary testing on their own, much like the testing required of the dairy industry?
It is a start, considering how dangerous Listeria can be.
Listeria monocytogenes is the bacteria responsible for listeriosis. This serious infection is often associated with contaminated food. In this case, packaged salads.
The CDC estimates that around 1,600 people become sick with listeriosis each year. About 260 of those die from the illness.
While anyone can become infected with Listeria, in many cases normally healthy people do not become seriously ill. There are certain groups, however, that are more at risk of becoming sick or experiencing more severe illness.
High-risk groups include:
Listeria bacteria cause a complicated range of symptoms. These symptoms, like most bacterial infections, can cause either mild or severe illnesses.
A uniquely dangerous complication, however, affects those who are pregnant.
Listeria infections generally cause intestinal illness. However, potential system-wide problems may develop if the bacteria leave the digestive system and attack other parts of the body.
One of the most common symptom profiles of Listeria illness involves intestinal illness. Intestinal illness occurs when the bacteria affect the digestive system.
Common symptoms include vomiting and diarrhea beginning within 24 hours of consuming something contaminated with Listeria bacteria. These symptoms are often resolved within three days.
Most people with intestinal Listeria illness do not require medical intervention or antibiotic treatment. Plenty of rest, fluids, and treating the symptoms is your best bet.
Intestinal Listeria illness can evolve to a more invasive illness.
Listeria bacteria cause invasive illness when they leave the digestive system and enter other parts of the body. Invasive listeriosis affects pregnant people and non-pregnant people in different ways. For both categories, invasive illness symptoms usually begin about two weeks after exposure.
While personal symptoms of invasive listeriosis are milder in pregnant people, the impact on the pregnancy poses potentially serious consequences. Someone who is pregnant and experiencing invasive listeriosis may have fever, fatigue, and muscle aches. However, listeriosis during pregnancy can lead to still birth, premature delivery, miscarriage, or life-threatening infection in the newborn.
Those who are not pregnant have a higher risk of serious illness or death. Invasive listeriosis in non-pregnant people often includes headaches, stiff neck, confusion, loss of balance, and convulsions. Some may also experience fever and/or muscle aches. This infection can be serious or even life-threatening. 1 in 20 nonpregnant people with invasive listeriosis will die from their illness.
If you have become sick with a Listeria infection, there are a few things you can do to help your situation.
If you have become sick from eating recalled products, get medical help right away. Even mild illnesses can escalate to dangerous or life-threatening infections. In addition to getting the help you need, reporting your illness can help others.
Unreported illnesses are not included in outbreak statistics. Your information and food diary can help narrow or expand the scope of a recall. An action that can help reduce the risk of spreading the outbreak to others. Others who may be more vulnerable to life-threatening complications.
As soon as you feel well enough, make a list of the foods you have eaten. Include as much detail as possible. The specific brands. Where did you get it? Where did you eat it? Was it at home, take home, or did you dine out? Are there others who may have consumed the same food? This information is important to outbreak investigators and can help them find other potential food sources responsible for the outbreak.
Medical bills, lost work, and other burdens associated with foodborne illness like Listeria add up. Who is responsible for those bills? What can you do? What are your rights?
All of these questions can be answered by an experienced Listeria Lawyer. Reach out to a Listeria Lawyer for advice as soon as possible.
If you have fallen sick with a Listeria infection, you may be eligible for legal compensation.
The Lange Law Firm, PLLC has helped many families with cases just like yours help hold accountable those responsible for foodborne illnesses. When a company becomes negligent, people become sick.
Call (833) 330-3663 or submit your information on the online submission form for a free consultation.
By: Heather Van Tassell (contributing writer, non-lawyer)
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