As of August 28, a total of 59 people infected with the outbreak strain of Listeria have been reported from 19 states – Including: Arizona 1, Florida 3, Georgia 2, Illinois 1, Indiana 1, Louisiana 1, Maryland 8, Massachusetts 3, Minnesota 1, Missouri 3, New Jersey 5, New Mexico 1, New York 17, North Carolina 1, Pennsylvania 2, South Carolina 2, Tennessee 1, Virginia 4, and Wisconsin 1.

Sick people’s samples were collected from May 29, 2024, to August 28, 2024.  Of 57 people with information available, all 59 have been hospitalized. One person got sick during their pregnancy and remained pregnant after recovering. So far, ten deaths have been reported, including one in Illinois, one in New Jersey, one in New York, one in Virginia, one in Florida, one in Tennessee, one in New Mexico, one in New York, and two in South Carolina.

Epidemiologic, laboratory, and traceback data show that Defendant’s meats which are sliced at delis, including Boar’s Head brand liverwurst, are contaminated with Listeria and are making people sick.

Defendant’s products sold at delis, especially those sliced or prepared at the delis, can be contaminated with ListeriaListeria spreads easily among deli equipment, surfaces, hands, and food. Refrigeration does not kill Listeria, but reheating to a high enough temperature before eating will kill any germs that may be on these meats.

Defendant published a recall of its deli meat products, including liverwurst and other deli meats, on July 26, 2024. The United States Department of Agriculture’s Food Safety and Inspection Service (FSIS) announced that Defendant expanded its July 26, 2024, recall of deli meat products that may be adulterated with Listeria monocytogenes on July 30, 2024.[1] Defendant is recalling approximately 7 million additional pounds of ready-to-eat meat and poultry products. Whole genome sequencing results show that a sample of Defendant’s liverwurst collected by the Maryland Department of Health tested positive for the outbreak strain of Listeria monocytogenes.

This recall expansion includes 71 products produced between May 10, 2024, and July 29, 2024, under Defendant’s Boar’s Head and Old Country brand names. These items include meat intended for slicing at retail delis as well as some packaged meat and poultry products sold at retail locations. These products have “sell by” dates ranging from 29-JUL-2024 through 17-OCT-24.

The products subject to recall were distributed to retail locations nationwide and some were exported to the Cayman Islands, Dominican Republic, Mexico, and Panama. The products shipped to retailers bear establishment number “EST. 12612” or “P-12612” inside the USDA mark of inspection on the product labels.

The problem was discovered when FSIS was notified that a liverwurst sample collected by the Maryland Department of Health tested positive for L. monocytogenes. The Maryland Department of Health, in collaboration with the Baltimore City Health Department, collected an unopened liverwurst product from a retail store for testing as part of an outbreak investigation of L. monocytogenes infections. Further testing determined the product sample tested positive for the outbreak strain. 

Beyond issues like paperwork lapses and leftover meat on equipment, the inspection records show inspectors faulted Defendant several times for mold and mildew building up in many locations throughout the company’s facility in Jarratt, Virginia. In July, federal inspectors found what looked to be mold and mildew around the hand washing sinks for the workers tasked with handling meats that are supposed to be ready to eat. Mold was also found building up outside of steel vats used by the plant, as well as in holding coolers between the site’s smokehouses. “A black mold like substance was seen throughout the room at the wall/concrete junction. As well as some caulking around brick/metal,” an inspector wrote in January, noting that some spots were “as large as a quarter.”

Other locations were found to have a number of issues with leaking and pooling water, including a puddle found with “a green algal growth” and condensation that was found to be “dripping over product being held.”

After inspectors flagged one of the leaks to the company, workers tried to mop up the leaks. “The employee wiped a third time, and the leaks returned within 10 seconds,” inspectors wrote after one condensation issue was raised on July 27, 2024, near fans that looked to be blowing the liquid onto uncovered deli meats.

In February, an inspector found “ample amounts of blood in puddles on the floor” and a “rancid smell” throughout a cooler used at the plant. A number of records also flag sightings of insects in and around deli meats at the plant, including one instance that prompted the agency to tag more than 980 pounds of ham in a smokehouse hallway to be “retained” for an investigation.

In June, another report flagged concerns over flies going in and out of “vats of pickle” left by Defendant in a room. “Small flying gnat like insects were observed crawling on the walls and flying around the room. The rooms walls had heavy meat buildup,” the report notes. Other parts of the facility were also found to have bugs, including what looked to be “ants traveling down the wall,” as well as a beetle and a cockroach.

Listeria is a gram-positive, rod-shaped bacterium that is ubiquitous and can grow under either anaerobic (without oxygen) or aerobic (with oxygen) conditions.

Listeriosis is one of the most important bacterial infections worldwide that arises mainly from the consumption of contaminated food.[2] The disease is caused by Listeria monocytogenes, which is considered an opportunistic pathogen that affects mainly those with underlying immune conditions, such as pregnant women, neonates, and elders, resulting in septicemia, meningitis, and/or meningoencephalitis. Of the six species of Listeria, only L. monocytogenes causes disease in humans. It thrives between bacteria 86-98.6oF (30-37oC), but Listeria can grow at temperatures as low as −0.4°C and survive in freezing conditions down to −18°C.[3] This unique quality allows thermal characteristics to be used as a means of differentiating Listeria from other possibly-contaminating bacteria. 

Listeria monocytogenes is omnipresent in nature; it is found widely in such places as water, soil, infected animals, human and animal feces, raw and treated sewage, leafy vegetables, effluent from poultry and meat processing facilities, decaying corn and soybeans, improperly fermented silage, and raw (unpasteurized) milk.[4]

Foodborne listeriosis is relatively rare but is a serious disease with high fatality rates (20%–30%) compared with other foodborne microbial pathogens. Severe L. monocytogenes infections are responsible for high hospitalization rates (91%) among the most common foodborne pathogens, may cause sporadic cases or large outbreaks, and can persist in food-processing environments and multiply at refrigeration temperatures, making L. monocytogenes a significant public health concern.[5]

Ready-to-eat foods are a notable and consistent source of Listeria. For example, a research study done by the ListeriaStudy Group found that L. monocytogenes grew from at least one food specimen in the refrigerators of 64% of persons with a confirmed Listeria infection (79 of 123 patients), and in 11% of more than 2,000 food specimens collected in the study. Moreover, 33% of refrigerators (26 of 79) contained foods that grew the same strain with which the individual had been infected, a frequency much higher than would be expected by chance. The danger posed by the risk of Listeria in ready-to-eat meats prompted the USDA to declare the bacterium an adulterant in these kinds of meat products and, as a result, to adopt a zero-tolerance policy for the presence of this deadly pathogen. The Code of Federal Regulations includes requirements for the post-lethality control of Listeria in meat and poultry products. This regulation is referred to as “The Listeria Rule,” which was enacted in 2003. The rule outlines prevention and control measures that must be taken in processing facilities to reduce the risk of contamination of ready-to-eat products.[6]

Listeria typically spreads to people through contaminated food or water but can also be transmitted from mother to fetus.

Except for the transmission of mother to fetus, human-to-human transmission of Listeria is not known to occur. Infection is caused almost exclusively by the ingestion of the bacteria, most often through the consumption of contaminated food. The most widely accepted estimate of foodborne transmission is 85-95% of all Listeria cases. 

The infective dose—that is, the number of bacteria that must be ingested to cause illness—is not known but is suspected to vary based on the strain. In an otherwise healthy person, an extremely large number of Listeria bacteria must be ingested to cause illness—estimated to be somewhere between 10-100 million viable bacteria (or colony forming units “CFU”) in healthy individuals, and only 0.1-10 million CFU in people at high risk of infection. Even with such a dose, a healthy individual will suffer only a fever, diarrhea, and related gastrointestinal symptoms.

The amount of time from infection to the onset of symptoms—typically referred to as the incubation period—can vary to a significant degree.[7]

According to the CDC, symptoms of Listeria infection can develop at any time from the same day of exposure to 70 days after eating contaminated food. According to the FDA, gastroenteritis (or non-invasive illness) has an onset time of a few hours to 3 days, while invasive illness can have an onset varying from 3 days to 3 months. According to one authoritative text:

The incubation period for invasive illness is not well established, but evidence from a few cases related to specific ingestions points to 11 to 70 days, with a mean of 31 days. In one report, two pregnant women whose only common exposure was attendance at a party developed Listeria bacteremia with the same uncommon enzyme type; incubation periods for illness were 19 and 23 days.

Adults can get listeriosis by eating food contaminated with Listeria, but babies can be born with listeriosis if their mothers eat contaminated food during pregnancy. The mode of transmission of Listeria to the fetus is either transplacental via the maternal bloodstream or ascending from a colonized genital tract. Infections during pregnancy can cause premature delivery, miscarriage, stillbirth, or serious health problems for the newborn. Pregnant women make up around 30% of all infection cases while accounting for 60% of cases involving the 10- to 40-year age group.

Several segments of the population are at increased risk and need to be informed so that proper precautions can be taken. The body’s defense against Listeria is called “cell-mediated immunity” because the success of defending against infection depends on our cells (as opposed to our antibodies), especially lymphocytes, otherwise known as “T-cells.” Therefore, individuals whose cell-mediated immunity is suppressed are more susceptible to the devastating effects of listeriosis, including HIV-infected individuals, who have been found to have Listeria-related mortality of 29%. The incidence of Listeria infection in HIV-positive individuals is higher than in the general population. One study found that:

The estimated incidence of listeriosis among HIV-infected patients in metropolitan Atlanta was 52 cases per 100,000 patients per year, and among patients with AIDS it was 115 cases per 100,000 patients per year, rates 65-145 times higher than those among the general population. HIV-associated cases occurred in adults who were 29-62 years of age and in postnatal infants who were 2 and 6 months of age.

Pregnant women naturally have a depressed cell-mediated immune system. While other systemic bacterial infections may result in adverse pregnancy outcomes at comparable frequencies, L. monocytogenes have notoriety because fetal complications largely occur in the absence of overt illness in the mother, delaying medical intervention. In addition, the immune systems of fetuses and newborns are very immature and are extremely susceptible to these types of infections. 

Other adults, especially transplant recipients and lymphoma patients, are given necessary therapies with the specific intent of depressing T-cells, and these individuals become especially susceptible to Listeria as well. Other adults, especially transplant recipients and lymphoma patients, are given necessary therapies with the specific intent of depressing T-cells, and these individuals become especially susceptible to Listeria as well.

According to the FDA, CDC, and other public health organizations, individuals at increased risk for being infected and becoming seriously ill with Listeria include the following groups:

  • Pregnant women: They are about 10-20 times more likely than other healthy adults to get listeriosis. About one-third of listeriosis cases happen during pregnancy. Fetuses are also highly susceptible to infection and severe complications.
  • Newborns: Newborns can develop life-threatening diseases from perinatal and neonatal infections
  • Persons with weakened immune systems 
  • Persons with cancer, diabetes, kidney, or gastrointestinal disease 
  • Persons with HIV/AIDS: Individuals with HIV/AIDS are almost 300 times more likely to get listeriosis than people with healthy immune systems. 
  • Persons who take glucocorticosteroid medications (such as cortisone) 
  • Persons of advanced age: One risk assessment showed people over 60 years old were 2.6 times more likely to develop listeriosis than the general population. And in 2011, the median age of diagnosed cases in people who were not pregnant was 71 years old. 

Only a small percentage of persons who ingest Listeria fall ill or develop symptoms. For those who do develop symptoms because of their infection, the resulting illness is either mild or quite severe, in what is sometimes referred to as a “bimodal distribution of severity.” [8] Listeria can cause two different types of disease syndromes with differing severity. Non-invasive Listeria infection causes gastroenteritis with symptoms such as diarrhea, nausea, and vomiting that resolve on their own. Healthy adults without any immunocompromising conditions typically experience this milder version of the disease. The more severe type of disease caused by Listeria monocytogenes is called listeriosis and is referred to as an invasive illness. 

On the mild end of the spectrum, listeriosis usually consists of the sudden onset of fever, chills, severe headache, vomiting, and other influenza-type symptoms. Along these same lines, the CDC notes that infected individuals may develop fever, muscle aches, and sometimes gastrointestinal symptoms such as nausea or diarrhea. When present, the diarrhea usually lasts 1-4 days (with 42 hours being average), with 12 bowel movements per day at its worst.

The more severe form of the illness occurs when the bacteria infect parts of the body that are typically sterile, such as the blood, brain, liver, and cerebral spinal fluid. The presence of the bacteria in these areas triggers the immune response and can lead to those more severe symptoms. L. monocytogenes has a specific affinity for the central nervous system (CNS), especially in cell-mediated immunodeficient individuals.[9]

As already noted, when pregnant, women have a mildly impaired immune system that makes them susceptible to Listeriainfection. If infected, the illness appears as acute fever, muscle pain, backache, and headache. The illness usually occurs in the third trimester, which is when immunity is at its lowest. Infection during pregnancy can lead to premature labor, miscarriage, infection of the newborn, or even stillbirth. Around twenty percent of such infections result in stillbirth or neonatal death. 

Newborns may present clinically with early-onset (less than 7 days) or late-onset forms of infection (7 or more days). Those with the early-onset form are often diagnosed in the first 24 hours of life with septicemia, meningitis, or respiratory distress and have a higher mortality rate. Early-onset listeriosis is most often acquired through trans-placental transmission. Late-onset neonatal listeriosis is less common and less severe than the early-onset form. Clinical symptoms may be subtle and include irritability, fever, poor feeding, and meningitis. The mode of acquisition of late onset listeriosis is poorly understood. 

For those persons who suffer a Listeria infection that does not resolve on its own, the complications can be numerous and possibly severe. The most common complication is septicemia (bacterial infection in the blood), with meningitis being the second most common. Other complications can include inflammation of the brain or brain stem (encephalitis), brain abscess, inflammation of the heart-membrane (endocarditis), septic arthritis, osteomyelitis (infection in the bone), and localized infection, either internally or of the skin. 

Death is the most severe consequence of listeriosis, and it is tragically common. The CDC has estimated that L. monocytogenes is the third leading cause of death from foodborne illness, with approximately 260 of 1,600 people diagnosed dying from their infections. For example, based on 2018 FoodNet surveillance data, 96% of 126 Listeria cases ended up in the hospital, the highest hospitalization rate for pathogenic bacterial infection. This data showed a fatality rate of 21%. According to the FDA, the case-fatality rate increases substantially based on complications, possibly reaching rates of 70% in cases with listeria meningitis, 50% in septicemia cases, and over 80% for perinatal/neonatal infections. In one US study, L. monocytogenes was reportedly the cause of nearly 4% of all cases of bacterial meningitis.


[1] https://www.fsis.usda.gov/recalls-alerts/boars-head-provisions-co–recalls-ready-eat-liverwurst-and-other-deli-meat-products

[2]           Reda, W. W., Abdel-Moein, K., Hegazi, A., Mohamed, Y., & Abdel-Razik, K. (2016). Listeria monocytogenes: An emerging food-borne pathogen and its public health implications. The Journal of Infection in Developing Countries10(02), 149-154. https://doi.org/10.3855/jidc.6616

[3]           Santos, T., Viala, D., Chambon, C., Esbelin, J., & Hébraud, M. (2019, May 24). Listeria monocytogenes Biofilm Adaptation to Different Temperatures Seen Through Shotgun Proteomics. https://www.frontiersin.org/articles/10.3389/fnut.2019.00089/full. 

[4]           Manning, A. (2019). Microbial Food Spoilage and Food Borne Diseases. In Food microbiology and food processing (pp. 125–130). Chapter 2. ED-TECH PRESS. 

[5]           Arslan, F., Meynet, E., Sunbul, M. et al. The clinical features, diagnosis, treatment, and prognosis of neuroinvasive listeriosis: a multinational study. Eur J Clin Microbiol Infect Dis 34,1213–1221 (2015). https://doi.org/10.1007/s10096-015-2346-5

[6]           USDA Staff. (2014, January 1). Controlling Listeria monocytogenes in Post-lethality Exposed Ready-to-Eat Meat and Poultry Products. https://www.fsis.usda.gov/wps/portal/fsis/topics/regulatory-compliance/guidelines/2014-0001.

[7]           Goulet V, King LA, Vaillant V, de Valk H. What is the incubation period for listeriosis? BMC Infect Dis. 2013; 13:11. Published 2013 Jan 10. doi:10.1186/1471-2334-13-11

[8]           Waldron, C. M. (2017, September 15). The Recovery and Transfer of Aerosolized Listeria Innocua. https://vtechworks.lib.vt.edu/handle/10919/78907. 

[9]           Arslan, F., Meynet, E., Sunbul, M., Sipahi, O. R., Kurtaran, B., Kaya, S., … Mert, A. (2015, June). The clinical features, diagnosis, treatment, and prognosis of neuroinvasive listeriosis: a multinational study. European journal of clinical microbiology & infectious diseases: official publication of the European Society of Clinical Microbiology. https://www.ncbi.nlm.nih.gov/pubmed/25698311.