--- title: Transmission of and Infection with Listeria date: 2012-07-12T15:39:00-07:00 author: admin canonical_url: "https://marlerclark.com/foodborne-illnesses/listeria/transmission-of-and-infection-with-listeria" section: Resource Library --- [Foodborne Illnesses](/foodborne-illnesses) / [Listeria](https://marlerclark.com/foodborne-illnesses/listeria) / # Transmission of and Infection with Listeria ### *Listeria* typically spreads to people through contaminated food or water, but can also be transmitted from mother to fetus. ![](https://s3.us-west-2.amazonaws.com/aboutlisteriacom-images/outbreaks/image5.jpeg)**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 amount 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. **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 blood stream 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. [ Next: Who is Most at Risk of Becoming Ill with Listeria? › ](https://marlerclark.com/foodborne-illnesses/listeria/who-is-most-at-risk-for-becoming-ill-with-listeria) ### More information about Listeria [August 23, 2023 ###### Listeria outbreak: Three die after drinking contaminated milkshakes Three people have died, and three others are in hospital after drinking milkshakes contaminated with listeria bacteria in the US state of Washington, health officials say. Marler Clark, the Listeria ... ](https://marlerclark.com/news_events/listeria-outbreak-three-die-after-drinking-contaminated-milkshakes) [July 12, 2023 ###### 2011 Listeria outbreaks linked to cantaloupes: A history A total of 148 persons infected with any of the five outbreak-associated strains of Listeria monocytogenes were reported to the CDC from 28 states. The number of infected persons identified ... ](https://marlerclark.com/news_events/2011-listeria-outbreak-linked-to-cantaloupes-a-history) [March 26, 2023 ###### Listeria linked to yogurt prompts recall Clio Snacks of Piscataway, New Jersey, is voluntarily recalling 581 cases of its Strawberry Granola & Greek Yogurt Parfait Bar due to potential contamination with Listeria monocytogenes, an organism which ... ](https://marlerclark.com/news_events/listeria-linked-to-yogurt-prompts-recall) [November 20, 2022 ###### Enoki Mushrooms recalled again As of November 15, 2022, two people infected with the outbreak strain of Listeria have been reported from two states. Sick people’s samples were collected from October 5, 2022, to October 8, 2022. ... ](https://marlerclark.com/news_events/enoki-mushrooms-recalled-again) [1. View all ](/news_events/outbreaks?illness=listeria&year=all) ## All Listeria Resources [###### Listeria Food Poisoning ](https://marlerclark.com/foodborne-illnesses/listeria/about-listeria) [###### The Incidence of Listeria Infections ](https://marlerclark.com/foodborne-illnesses/listeria/the-incidence-of-listeria-infections) [###### The Prevalence of Listeria in Food and the Environment ](https://marlerclark.com/foodborne-illnesses/listeria/listeria-prevalence) [###### Transmission of and Infection with Listeria ](https://marlerclark.com/foodborne-illnesses/listeria/transmission-of-and-infection-with-listeria) [###### Who is Most at Risk of Becoming Ill with Listeria? ](https://marlerclark.com/foodborne-illnesses/listeria/who-is-most-at-risk-for-becoming-ill-with-listeria) [###### What Are the Symptoms of Listeria Infection? ](https://marlerclark.com/foodborne-illnesses/listeria/listeria-symptoms-risks) [###### Complications of Listeria Infection ](https://marlerclark.com/foodborne-illnesses/listeria/complications-of-listeria-infection) [###### How is Listeria Infection Diagnosed? ](https://marlerclark.com/foodborne-illnesses/listeria/listeria-diagnosis) [###### Treatment for Listeria Infection ](https://marlerclark.com/foodborne-illnesses/listeria/listeria-treatment) [###### Antimicrobial Resistance in Bacteria ](https://marlerclark.com/foodborne-illnesses/listeria/antimicrobial-resistance-in-bacteria) [###### The Economic Impact of Listeria Infections ](https://marlerclark.com/foodborne-illnesses/listeria/the-economic-impact-of-listeria-infections) [###### Preventing Listeria Infection ](https://marlerclark.com/foodborne-illnesses/listeria/listeria-prevention) [###### Listeria References ](https://marlerclark.com/foodborne-illnesses/listeria/listeria-references) ### Other foodborne illnesses [E. coli](https://marlerclark.com/foodborne-illnesses/e-coli) [Salmonella](https://marlerclark.com/foodborne-illnesses/salmonella) [Hepatitis A](https://marlerclark.com/foodborne-illnesses/hepatitis-a) [Reactive Arthritis](https://marlerclark.com/foodborne-illnesses/reactive-arthritis) [Guillain-Barre Syndrome](https://marlerclark.com/foodborne-illnesses/guillain-barre-syndrome) [Irritable Bowel Syndrome](https://marlerclark.com/foodborne-illnesses/irritable-bowel-syndrome) [Norovirus](https://marlerclark.com/foodborne-illnesses/norovirus) [Botulism](https://marlerclark.com/foodborne-illnesses/botulism) [Campylobacter](https://marlerclark.com/foodborne-illnesses/campylobacter) [Shigella](https://marlerclark.com/foodborne-illnesses/shigella) [Cyclospora](https://marlerclark.com/foodborne-illnesses/cyclospora) [Hemolytic Uremic Syndrome](https://marlerclark.com/foodborne-illnesses/hemolytic-uremic-syndrome)