Signs and Symptoms of Listeria Infection

Medically reviewed by Mary Josephine Hessert, DO

Listeria infection, or listeriosis, is a serious but uncommon foodborne illness that develops after eating food contaminated with Listeria monocytogenes bacteria. In otherwise healthy people, the infection causes flu-like symptoms such as diarrhea, fever, muscle pain, and headache within a few hours or up to three days after eating contaminated food.

Pregnant people, infants, older adults, and people with weakened immune systems are vulnerable to a more severe Listeria infection known as invasive listeriosis. In these high-risk groups, the bacteria can spread from the intestines into the bloodstream, affecting any body part, including the brain and spinal cord. Symptoms of invasive listeriosis can take three days to three months to develop and can include fever, muscle aches, confusion, stiff neck, balance problems, and seizures (convulsions).

Depending on the type and severity of listeriosis, symptoms can last for days to several weeks.

Noninvasive Listeriosis (Listeria Infection) Symptoms

Listeria infections are rare in healthy, non-pregnant people unless they ingest high amounts of Listeria bacteria in contaminated foods. Many people can consume small amounts of Listeria bacteria and not become ill. In those who develop noninvasive listeriosis, symptoms will begin within hours to three days after eating contaminated foods—usually within 24 hours—and last 1 to 3 days. 

Noninvasive listeriosis (febrile listerial gastroenteritis) affects the gastrointestinal (GI) system and usually causes mild symptoms that resolve without treatment. Symptoms can include: 

• Diarrhea (loose, watery stools)

• Fever

• Chills

• Headache

• Myalgia (muscle aches)

• Abdominal pain

• Nausea and vomiting
  

In rare cases, febrile listeria gastroenteritis (noninvasive listeriosis) can progress to invasive listeriosis, especially in high-risk groups (e.g., older adults).

Invasive Listeriosis (Listeria Infection) Symptoms

Invasive listeriosis occurs when the Listeria bacteria spread beyond the intestines and into the bloodstream, where the bacteria can travel to and affect the brain, meninges (membranes surrounding the brain and spinal cord), and other organs.

Older adults, pregnant people, and people with chronic diseases or weakened immune systems—including those with HIV, diabetes, and cancer—are more likely to develop invasive listeriosis.

Symptoms of invasive listeriosis can take up to two months to develop but usually appear within several days after eating contaminated foods. Symptoms can be severe and may include:

• Fever

• Muscle aches

• Fatigue

• Severe headache

• Confusion

• Stiff neck

• Loss of balance

• Vomiting

• Seizures
  

Symptoms of invasive listeriosis can vary, depending on which body system or organ the infection affects. Listeria infection can affect the brain, meninges, heart, bloodstream, and lungs.

• Meningitis: Develops when Listeria bacteria affect the membranes surrounding the brain and spinal cord (meninges). Symptoms include fever, headache, stiff neck, nausea, vomiting, sensitivity to light, and confusion.

• Encephalitis: Inflammation of the brain from Listeria infection causes symptoms like sudden fever, severe headache, vomiting, confusion, drowsiness, and seizures.

• Endocarditis: When Listeria bacteria travel to the heart, endocarditis—inflammation of the lining of the heart’s valves and chambers—can cause symptoms such as fever and chills, chest pain, joint, muscle, and back pain, night sweats, shortness of breath, skin changes, and cough.

• Pneumonia: Listeria that affects the lungs can cause pneumonia, leading to symptoms such as fever, cough (with mucus), chest pain, shortness of breath, nausea, vomiting, and diarrhea.

• Bacteremia: When Listeria enters the bloodstream (bacteremia), symptoms such as rapid breathing, shaking chills, fever, altered consciousness (confusion), low blood pressure, abdominal pain, diarrhea, nausea, and vomiting can occur.
  

Symptoms in Pregnant People

Pregnant people are ten times more likely than others to get listeriosis. The infection poses a serious threat to the health of fetuses, increasing the risk of miscarriage, preterm delivery, stillbirth, and life-threatening illness in newborns.

Symptoms of Listeria infection are generally mild in pregnant people, and some have no symptoms at all. When symptoms occur, they are flu-like and can include:

• Fever

• Chills

• Muscle aches

• Joint pain

• Fatigue

• Diarrhea

• Upset stomach

• Headache

Symptoms in Infants

Listeria infections can affect fetuses and newborns when a pregnant parent passes the infection onto their baby before, during, or after birth. Listeriosis is a serious illness in newborns. It is categorized into two types, depending on when symptoms first appear:

• Early onset: Symptoms appear within the first hours or days after birth.

• Delayed (late) onset: Symptoms develop within one to several weeks after birth. 
  

Symptoms of listeriosis in infants can include:

• Listlessness (e.g., sluggish, drowsiness, sleepy)

• Vomiting

• Jaundice (yellow-tinted eyes and skin)

• Skin rash

• Breathing problems (e.g., rapid breathing, grunting)

• Poor appetite

When to Contact a Healthcare Provider

Listeria infections are rare in the United States but can cause serious illness. The Centers for Disease Control and Prevention (CDC) recommends people contact their healthcare provider if both of the following apply:

• You ate food linked to a Listeria outbreak or the food has been recalled, AND

• You develop symptoms of listeriosis, such as fever, fatigue, muscle aches, and diarrhea

If you belong to a high-risk group (are pregnant, 65 years or older, or have a weakened immune system), it is especially important to seek immediate medical attention if you suspect you may have listeriosis. Early diagnosis and treatment can help prevent life-threatening complications.

Seek immediate medical care if you experience symptoms of invasive listeriosis, including:

• Stiff neck

• Loss of balance

• Confusion or changes in mental status

• Seizures

• Severe headache

Questions to Ask Your Provider

When you visit your healthcare provider with concerns about Listeria infection, open communication can help ensure you get the information you need. You may consider asking:

• Based on my symptoms, what is the likelihood I have a Listeria infection rather than another foodborne illness (e.g., Salmonella)?

• What treatment options are available for listeriosis?

• How long will my fever last?

• Are there medicines I can take to reduce the frequency of diarrhea?

• Are there complications of Listeria infection I should be aware of?

A Quick Review

Listeria infection, or listeriosis, is an uncommon foodborne illness. Listeriosis can cause gastrointestinal illness and symptoms like fever, diarrhea, muscle aches, and vomiting in otherwise healthy people. Listeriosis can pose serious risks for pregnant people and their unborn babies, older adults, and people with weakened immune systems.

When Listeria bacteria enter the bloodstream, they can invade and affect the brain, spinal cord, heart, and other body systems and organs, causing symptoms like severe headache, stiff neck, confusion, loss of balance, and seizures. 

Contact your healthcare provider if you develop symptoms of listeriosis or have concerns about food you recently ate that may have been contaminated with Listeria bacteria.

Frequently Asked Questions

Does listeria go away on its own?

In otherwise healthy people, mild gastrointestinal Listeria infections often resolve without treatment within three days. People in high-risk groups — including pregnant people, older adults, and people with weakened immune systems—should seek medical attention and treatment to prevent complications.

What foods should you avoid if you have listeria?

People with mild Listeria infection symptoms, such as diarrhea and fever, should drink plenty of water and eat plain foods, such as saltine crackers, to restore lost fluids and electrolytes and prevent dehydration.

Certain foods are more likely to contain Listeria monocytogenes bacteria and increase the risk of Listeria infection, including unpasteurized milk, soft cheeses (e.g., brie), pre-made salads, deli meats (e.g., hot dogs, cold cuts), and smoked seafood. 

Can listeria spread from person to person?

No, listeria is not contagious and does not spread from person to person. However, pregnant people can transmit Listeria to their fetuses before, during, or after birth. Most people get sick with Listeria after eating foods contaminated with Listeria monocytogenes bacteria.

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