Read condition-specific symptoms and clinical context for Listeria monocytogenes. A foodborne bacterium that most people shrug off but that can cause severe illness in pregnancy, newborns and older adults.
PHAC describes L. monocytogenes as a Gram-positive, non-spore forming, rod-shaped coccobacillus measuring 0.5 to 2 micrometres long and 0.5 micrometres in diameter, able to reproduce at temperatures between 1 and 45 degrees Celsius and across pH values from 4.3 to 9.6 — which is why refrigeration does not stop it. CDC estimates that 1,250 people are infected with Listeria and 172 people die from the infection each year in the United States, and describes it as the fourth leading cause of death from foodborne illness there. CDC also states that people outside the higher-risk groups can be infected but rarely become seriously ill, so the same organism produces very different outcomes depending on who eats it.
CDC states that symptoms of invasive illness usually start within 2 weeks after eating food contaminated with Listeria, and lists a different, milder symptom set for pregnant women than for other people.
Possible symptoms: Fever; Flu-like symptoms such as muscle aches and fatigue.
PHAC records transplacental transmission as a route and gives neonatal mortality of 20 to 30%. Anyone who is pregnant and concerned about a food exposure should speak with their own healthcare provider; this app does not assess an individual pregnancy.
CDC lists a broader symptom set for invasive illness in people who are not pregnant, again usually starting within 2 weeks after eating contaminated food. PHAC records central nervous system infection, with meningitis the most frequently recognised form.
Possible symptoms: Fever; Flu-like symptoms such as muscle aches and fatigue; Headache; Stiff neck; Confusion; Loss of balance; Seizures.
PHAC reports that mortality approaches 50% in human cases of listeriosis. That figure describes recognised, mostly invasive cases rather than everyone exposed. Suspected illness needs clinical assessment and treatment.
CDC describes a separate, milder intestinal illness whose symptoms usually start within 24 hours after eating contaminated food and usually last 1 to 3 days. PHAC separately describes febrile gastroenteritis.
Possible symptoms: Diarrhea; Vomiting.
CDC describes this form as usually lasting 1 to 3 days. Severe or prolonged illness, and any illness in a higher-risk group, needs medical advice.
Eating food that contains Listeria does not always lead to recognised illness.
CDC states that people outside the higher-risk groups can be infected with Listeria but rarely become seriously ill. The bundled sources give no symptom list for exposure without illness, and none is invented here. This profile also does not assign a long-term human carriage state: PHAC describes the organism in food, soil and animal hosts rather than as a normal member of the human microbiota.
Food-safety questions about a product and clinical questions about a person are separate. Recall and food-handling advice comes from food-safety authorities; symptoms are assessed clinically.
Source check: 2026-09-20. Educational content; independent scientific review remains pending.