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Definition & Symptoms

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Listeria: Food Poisoning's Rare but Deadly Germ
February 27, 2012
Dr. Benjamin Silk presents key information on listeriosis in the aftermath of the large 2011 outbreak.

What is Listeriosis?

Listeriosis, a serious infection usually caused by eating food contaminated with the bacterium Listeria monocytogenes 1, is an important public health problem in the United States 2. The disease primarily affects older adults, pregnant women, newborns, and adults with weakened immune systems 3. However, rarely, people without these risk factors can also be affected. The risk may be reduced by following a few simple recommendations.

What are the Symptoms of Listeriosis?

A person with listeriosis usually has fever and muscle aches, sometimes preceded by diarrhea or other gastrointestinal symptoms. Almost everyone who is diagnosed with listeriosis has "invasive" infection, in which the bacteria spread beyond the gastrointestinal tract. The symptoms vary with the infected person:

  • Pregnant women: Pregnant women typically experience fever and other non-specific symptoms, such as fatigue and aches. However, infections during pregnancy can lead to miscarriage, stillbirth, premature delivery, or life-threatening infection of the newborn 3,4.
  • People other than pregnant women: Symptoms can include headache, stiff neck, confusion, loss of balance, and convulsions in addition to fever and muscle aches.

Listeriosis can present in different ways. In older adults and people with immunocompromising conditions, septicemia and meningitis are the most common clinical presentations 2. Pregnant women may experience a fever and other non-specific symptoms, such as fatigue and aches, followed by fetal loss or bacteremia and meningitis in their newborns 3,4. Immunocompetent people may experience acute febrile gastroenteritis or no symptoms 5,6.


  1. Schlech WF, 3rd, Lavigne PM, Bortolussi RA, Allen AC, Haldane EV, Wort AJ, Hightower AW, Johnson SE, King SH, Nicholls ES, Broome CV. Epidemic listeriosis--evidence for transmission by food. The New England journal of medicine. 1983;308(4):203-6.
  2. Silk BJ, Date KA, Jackson KA, Pouillot R, Holt KG, Graves LM, Ong KL, Hurd S, Meyer R, Marcus R, Shiferaw B, Norton DM, Medus C, Zansky SM, Cronquist AB, Henao OL, Jones TF, Vugia DJ, Farley MM, Mahon BE. Invasive listeriosis in the Foodborne Diseases Active Surveillance Network (FoodNet), 2004-2009: further targeted prevention needed for higher-risk groups. Clinical infectious diseases : an official publication of the Infectious Diseases Society of America. 2012;54 Suppl 5:S396-404.
  3. Painter J & Slutsker L. Listeriosis in humans. In: E. T. Ryser & E. H. Marth., editor. Listeria, Listeriosis and Food Safety 3rd ed Boca Raton, Florida: Taylor and Francis Group; 2007. p. 85-110.
  4. Jackson KA, Iwamoto M, Swerdlow D. Pregnancy-associated listeriosis. Epidemiology and infection. 2010;138(10):1503-9.
  5. Riedo FX, Pinner RW, Tosca ML, Cartter ML, Graves LM, Reeves MW, Weaver RE, Plikaytis BD, Broome CV. A point-source foodborne listeriosis outbreak: documented incubation period and possible mild illness. The Journal of infectious diseases. 1994;170(3):693-6.
  6. Dalton CB, Austin CC, Sobel J, Hayes PS, Bibb WF, Graves LM, Swaminathan B, Proctor ME, Griffin PM. An outbreak of gastroenteritis and fever due to Listeria monocytogenes in milk. The New England journal of medicine. 1997;336(2):100-5.