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Overview

What Is Listeriosis?

Listeriosis is a foodborne infection caused by the bacterium Listeria monocytogenes. It may cause a mild intestinal illness with diarrhea and vomiting, or it can spread beyond the intestines and cause serious invasive disease. Pregnant people, newborns, adults age 65 or older, and people with weakened immune systems have a higher risk of severe illness. Although listeriosis is uncommon, it can lead to serious complications in these groups.

Symptoms

Listeriosis Symptoms

Listeriosis symptoms may begin days or weeks after exposure, and the timing can vary. Symptoms depend on whether the infection remains in the intestines or becomes invasive, as well as the person’s age and overall health.

  • Fever may occur with intestinal or invasive listeriosis.
  • Muscle aches can cause generalized soreness.
  • Fatigue may feel more intense than usual.
  • Nausea can occur with or without other digestive symptoms.
  • Vomiting may develop after eating contaminated food.
  • Diarrhea is a common symptom of intestinal illness.
  • Headache may occur with a more widespread infection.
  • A stiff neck can be a sign of inflammation around the brain and spinal cord (meningitis).
  • Confusion may occur when infection affects the nervous system.
  • Loss of balance (ataxia) can occur with neurologic involvement.
  • Seizures are a serious symptom of possible brain or nervous system infection.

Pregnancy and newborns

Contact a healthcare professional promptly

A pregnant person with fever or flu-like symptoms after a possible contaminated-food exposure should contact a healthcare professional promptly, even if symptoms seem mild. A newborn with fever, poor feeding, unusual sleepiness, breathing problems, or other concerning symptoms also needs prompt medical assessment.

How It Spreads

How Listeriosis Spreads

Listeria infection most often occurs after eating food contaminated with Listeria monocytogenes. Unlike many bacteria, Listeria can survive and grow at refrigerator temperatures, so refrigeration does not make contaminated food safe.

  • Ready-to-eat refrigerated foods, such as deli meats, soft cheeses, or prepared salads, can carry Listeria if contaminated.
  • Unpasteurized milk and dairy products may contain Listeria.
  • Contaminated produce or meats can cause infection when eaten or handled.
  • Cross-contamination can occur when raw foods, utensils, or surfaces spread bacteria to ready-to-eat foods.
  • Transmission can occur from a pregnant person to the fetus during pregnancy or to the newborn around birth.

Risk Factors

Who Is at Higher Risk for Listeriosis

  • Pregnancy increases the risk of infection-related complications for the fetus, even when the pregnant person has mild symptoms.
  • Newborns are at increased risk of serious listeriosis because infection can occur during pregnancy or birth.
  • Adults age 65 or older have a higher risk of invasive infection.
  • A weakened immune system, including from cancer, HIV, or an organ transplant, increases the risk of severe disease.
  • Certain chronic conditions and immune-suppressing medicines can make listeriosis more likely to become invasive.
  • Eating unpasteurized milk, cheese, or other products increases exposure risk.
  • Eating high-risk refrigerated ready-to-eat foods without following food-safety guidance can increase exposure risk.
  • Unsafe food storage or handling, including cross-contamination and ignoring storage instructions, can allow Listeria to spread.

Complications

Listeriosis Complications

Complications are more likely when Listeria enters the bloodstream or nervous system, particularly in people at higher risk. Invasive listeriosis can become life-threatening and may require hospital care.

  • A bloodstream infection (bacteremia) can spread Listeria throughout the body.
  • Meningitis or meningoencephalitis can cause inflammation around the brain and spinal cord.
  • Sepsis is a dangerous, body-wide response to infection.
  • Pregnancy-associated listeriosis can lead to pregnancy loss.
  • Infection during pregnancy can result in premature birth.
  • Listeriosis can cause stillbirth.
  • A newborn may develop a serious infection affecting the blood, lungs, or nervous system.

Diagnosis

How Listeriosis Is Diagnosed

When listeriosis is suspected, clinicians review symptoms, possible food exposure, pregnancy status, underlying conditions, and examination findings. Symptoms alone cannot confirm the infection, so laboratory testing is used when clinically appropriate.

  • A blood culture can identify Listeria in people with suspected bloodstream infection.
  • Cerebrospinal fluid testing may be performed when meningitis or another nervous system infection is suspected.
  • Pregnancy or newborn specimens may be tested when the clinical situation suggests listeriosis.

Treatment & Management

Listeriosis Treatment and Management

Treatment depends on the form and severity of illness. Mild intestinal illness may sometimes be managed with medical guidance, while invasive infection or illness in a high-risk person requires prompt evaluation and prescription treatment, including listeriosis antibiotics when indicated.

  • Clinician-directed antibiotic therapy is used when treatment is needed, especially for invasive or high-risk infection.
  • Severe infection may require hospital care for close monitoring and treatment of complications.
  • Intravenous fluids and other supportive measures may be used for dehydration or serious illness.
  • Pregnancy and newborn infections require individualized management by healthcare professionals.

Treatment safety

Do not self-treat with leftover antibiotics

Do not use leftover antibiotics or someone else’s prescription. Seek medical advice promptly if symptoms occur after a concerning food exposure or in a person at higher risk of invasive listeriosis.

Prevention

How to Prevent Listeriosis

  • Choose pasteurized milk, cheese, and other dairy products.
  • Avoid high-risk foods when food-safety guidance recommends avoiding them, especially during pregnancy or for people with weakened immunity.
  • Wash hands with soap and water before preparing food and after handling raw foods.
  • Wash fresh produce under running water before eating or preparing it.
  • Prevent cross-contamination by keeping raw foods separate from ready-to-eat foods and cleaning surfaces and utensils.
  • Cook foods thoroughly according to safe cooking guidance.
  • Keep the refrigerator cold and store foods promptly.
  • Follow use-by dates and the storage instructions on food labels.

Outlook and Prognosis

Outlook and Prognosis for Listeriosis

Many mild intestinal infections improve without serious complications, while invasive listeriosis can require hospitalization and may have a prolonged or serious course. Recovery depends on the type and location of infection, the person’s health, and how quickly effective treatment begins.

  • Infection limited to the intestines generally has a better outlook than infection in the blood or nervous system.
  • Older age can increase the risk of severe illness and a more difficult recovery.
  • Pregnancy or newborn status affects the risks to both the pregnant person and the developing or newly born child.
  • Weakened immune function can make infection harder to control.
  • Underlying health conditions can influence complications and recovery.
  • Starting effective treatment quickly can improve the chance of recovery when invasive disease is present.

When Should You See a Doctor

When Should You See a Doctor for Listeriosis?

Call a healthcare professional

Get prompt medical advice

Contact a healthcare professional promptly for fever or flu-like symptoms during pregnancy, symptoms after a suspected contaminated-food exposure in a high-risk person, or persistent vomiting or diarrhea.

Seek emergency care

Act quickly for severe symptoms

Seek emergency care for a stiff neck, confusion, seizures, trouble staying awake, difficulty breathing, signs of sepsis, or a severely ill newborn.

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