24 Signs and Symptoms of Listeria (Listeriosis)
If you’ve eaten deli meats, soft cheeses, or ready-to-eat foods and feel unwell afterward, you might be wondering whether your symptoms are cause for concern.
Listeria infection is a complex foodborne illness that often develops without immediate symptoms. It may go unnoticed in healthy individuals or cause only mild digestive symptoms until it becomes invasive and causes serious symptoms.
However, the infection can cause serious and potentially life-threatening complications in pregnant women or newborns, in particular.
This article highlights key warning signs to consider, identifies at-risk individuals, and explains when to see a doctor to avoid serious health issues.
Common Symptoms of Mild Listeria
If you accidentally consume food contaminated with Listeria monocytogenes, the bacterium responsible for listeriosis, the infection may develop gradually and easily dismissed as a stomach discomfort.
Listeria can spread during food processing, storage, or handling and is commonly identified in pre-packaged salads, raw sprouts, and unpasteurized dairy products.
Signs can appear as soon as 24 hours but may take days or even weeks to develop, depending on the individual’s immune response and the level of contamination. In mild cases, listeriosis typically lasts 1–3 days and resolves without complications.
Fever and Chills
Your body temperature may rise to 100.4°F (38°C) or higher as your immune system responds to the infection. The fever may fluctuate in intensity, sometimes worsening in the evening or temporarily subsiding with rest, over-the-counter medication, or hydration.
Chills often occur before or during fever spikes, causing sudden sensations of cold and uncontrollable shivering. These episodes may last briefly and can repeat as the fever progresses.
Sweating, muscle aches, and fatigue may accompany the fever, contributing to overall discomfort. Some individuals may also experience dizziness or headaches as their bodies cope with temperature changes while fighting the infection.
Muscle Aches and Weakness
Your muscles might feel sore and tender, similar to how you feel with the flu. The discomfort may feel dull and throbbing, or present as stiffness after periods of inactivity, impacting your entire body, particularly your back, legs, and shoulders.
Muscle weakness can make simple tasks feel more difficult, such as standing for long periods or lifting objects. Some individuals also experience mild muscle cramps or joint discomfort, along with fatigue and low energy.
Diarrhea
Contaminated food can upset your digestive system within hours to a few days, causing loose or watery stools. This bowel activity may become frequent, urgent, or unpredictable, sometimes occurring several times daily.
Mild to moderate stomach cramps may accompany diarrhea, often feeling like waves of discomfort in the lower abdomen while you are in the toilet. Some individuals may also experience bloating, gas, nausea, or a sense of incomplete bowel emptying.
Nausea and Vomiting
You might feel queasy or sick to your stomach within a few hours of eating contaminated food. This uneasiness can range from mild queasiness to severe unease, sometimes triggered or worsened by eating, movement, or certain smells.
Vomiting may accompany the uncontrolled nausea, occurring intermittently and varying in intensity. This discomfort may be accompanied by abdominal cramping or a general sense of illness.
Stomach Pain
Abdominal discomfort may feel dull, cramping, or aching, and is most commonly felt in the lower abdomen. This pain may develop gradually or suddenly, sometimes worsening after eating.
It may also occur with other digestive symptoms that affect your appetite and desire to drink fluids, leading to an overall feeling of discomfort.
Symptoms in Pregnant Women
A weakened immune response makes pregnant women more vulnerable to listeria infection. Mild symptoms can still be serious, as the infection can cross the placenta and affect the baby.
Flu-Like Symptoms
If you are pregnant and infected with listeria, you may experience flu-like symptoms that feel more intense and persistent than usual, and may be associated with a viral illness.
Unlike mild fevers in non-high-risk individuals, your fever may be prolonged and typically ranges from 100.6°F to 102.5°F (38.1°C to 39.2°C) and may fluctuate throughout the day.
Chills can occur in waves, causing shivering and a sensation of coldness even in warm conditions. Sweating, particularly at night, may follow fever spikes and leave you feeling damp or overheated.
As your body fights the infection, you may also develop a headache, which can range from mild discomfort to intense pain.
You may also experience muscle aches and overwhelming fatigue. You might notice your body feeling unusually weak, with aches that don’t seem to go away.
Stomachache
You may feel abdominal pain or cramping in the lower stomach or pelvic area, which can feel similar to Braxton Hicks contractions or typical pregnancy discomfort.
Unlike those in the non-high-risk population, pregnant women may feel more intense and persistent stomach pain. Instead of mild discomfort, you might have sharp cramps, bloating, or nausea that lasts longer than typical morning sickness.
Some women develop a sudden loss of appetite, as eating worsens your stomachache, making meals uncomfortable or unappealing. In some cases, diarrhea may also occur, increasing the risk of dehydration, which is especially concerning during pregnancy.
Reduced Fetal Movement
If you are pregnant and have listeriosis, you may notice your baby moving less than usual. Unlike normal variations in fetal activity, a significant decrease or prolonged stillness could indicate distress, as the infection may affect the placenta and your baby’s oxygen supply.
You might feel fewer kicks, rolls, or flutters, making you anxious about your baby’s well-being. If you notice reduced fetal movements, try stimulating activity by eating, drinking something cold or sugary, or lying on your left side in a quiet place.
Fetal movements usually resume within 30 minutes to two hours after stimulation. Monitor how long it takes to detect 10 movements within this period.
If movement doesn’t return to normal or continues to decrease, get medical help immediately. Unlike temporary changes in movement, persistent inactivity could signal a problem.
Symptoms in Babies
Newborns with listeriosis often show serious symptoms that require immediate medical attention. They can acquire the infection in the womb or during birth, leading to complications affecting breathing, feeding, and responsiveness.
Poor Feeding
Poor feeding is often one of the earliest signs of neonatal Listeria infection, as it can impair nerve and muscle function, resulting in weak sucking reflexes and difficulty swallowing.
They may turn away bottled or breast milk, take longer to feed, or tire quickly, leading to inadequate nutritional intake. Some babies may cry or become frustrated during feeding attempts, indicating further discomfort.
Be alert for signs of dehydration, such as fewer than six wet diapers in 24 hours, dry mouth, or unusual drowsiness. If these signs appear, seek immediate medical attention to prevent complications.
Irritability
Babies with Listeria infection may become unusually fussy, restless, or difficult to soothe, even after feeding or attending to their needs.
Their cry may be weaker, higher-pitched, or whimper more than usual. Your baby may cry while arching its back, pulling its legs up, or appearing stiff or floppy, indicating discomfort.
They may also wake up frequently, struggle to fall asleep, or seem excessively drowsy between periods of fussiness. Additionally, some babies may feel unusually hot or cold, suggesting temperature instability, which can further contribute to their irritability.
Difficulty Breathing
Breathing difficulties in babies with listeria infection can indicate serious complications such as sepsis or pneumonia. Watch for fast, irregular, or labored breathing, as well as gasping, shallow breaths, or pauses in breathing.
Signs of respiratory distress include grunting, wheezing, nasal flaring, and abdominal retractions during breathing. A weak cry, extreme drowsiness, and poor responsiveness indicate low oxygen levels.
Pale or bluish skin, especially around the lips or fingertips, is a critical warning sign of oxygen deprivation. If your baby exhibits any of these symptoms, seek urgent medical attention immediately to avoid potentially life-threatening outcomes.
Seizures
Seizures in babies with listeria infection may occur with a cluster of signs, often accompanied by fever, irritability, feeding difficulties, or breathing problems.
Babies may show jerking movements, sudden stiffness in their arms and legs, or subtle signs like facial twitches, repeated chewing, or unusual eye movements like blank staring or rolling their eyes back.
Some may also pause their breathing for a short time before or after a seizure. Watch for abnormal movements, including cycling of the legs or arms, sudden floppiness, or brief episodes of stillness and unresponsiveness.
Invasive Listeriosis Symptoms
Invasive listeriosis occurs when bacteria spread beyond the digestive tract, spreading to the bloodstream or nervous system. Without immediate medical treatment, this condition can lead to life-threatening complications, including brain inflammation or blood infection.
High Fever
Your body temperature may rise above 101.5°F (38.6°C) as your immune system responds to the infection. Unlike mild fevers, a high fever from invasive listeriosis tends to be persistent and less responsive to standard fever-reducing medications.
Chills can become more intense, leading to episodes of uncontrollable shivering that may last longer and occur more frequently. Excessive sweating often follows as your body attempts to regulate its temperature, which may lead to dehydration.
With a prolonged high fever, you may experience pronounced muscle aches, extreme fatigue, and other symptoms that show the disease’s progression.
Severe Headache
The headache from invasive listeriosis is often severe and persistent, different from regular headaches. It might feel throbbing, pressure-like, or intense, and worsen with movement, bright lights, or loud sounds.
The pain often does not improve despite over-the-counter medication. You may also experience additional signs of brain inflammation or blood infection.
Stiff Neck
A stiff neck from listeriosis makes moving your head forward, backward, or side to side painful. The discomfort may feel sharp, aching, or heavy, with severe headaches often accompanying it.
Stiffness results from inflammation in the muscles and tissues surrounding the brain and spinal column due to a meningitis infection. If you can’t touch your chin to your chest because of stiffness, it might signal a serious medical problem that requires immediate attention.
Confusion
Mental confusion can range from mild disorientation to severe mental impairment. Family members may notice these changes before you do, as confusion can initially be subtle.
You may have difficulty focusing on simple tasks or conversations, and your thinking may feel foggy. Confusion may progress to the point where it is hard to remember recent events or recognize familiar people.
Some individuals may also have trouble finding the right words to say, or lose track of what they are saying. It can come and go and worsen over time, often making daily activities difficult.
Loss of Balance
You may feel physically unbalanced while standing still, and walking could become increasingly challenging as your perception of space and depth changes.
Some people also experience a sensation of “floating” or “swaying,” even while sitting or lying down, making even small movements feel risky.
As the condition worsens, you may feel dizzy or like the room is spinning, making it difficult to stabilize yourself.
Seizures
Seizures from listeriosis can range from brief memory lapses to full-body convulsions. They occur when the infection disrupts the brain’s normal electrical patterns, which can develop suddenly.
Before a seizure begins, you might experience warning signs such as tingling sensations in the limbs, visual disturbances, or an unexplained sense of confusion.
Some seizures cause blank staring or involuntary muscle twitches, while others lead to rapid, rhythmic jerking or muscle rigidity.
More intense seizures can lead to a complete loss of consciousness. If someone nearby experiences a seizure, monitor its duration and frequency—this information is critical during medical evaluation and treatment.
Low Blood Pressure
Listeria can cause a systemic infection that lowers blood pressure, reducing oxygen and blood flow to vital organs. In response, your heart may beat faster or irregularly as it tries to stabilize blood flow.
Poor blood flow can lead to tissue and organ damage. If your symptoms worsen, it signals a medical emergency requiring immediate intervention.
Rapid Heartbeat
As your body fights the infection, your heart rate may rise above 100 beats per minute, known as tachycardia. This fast heartbeat often feels like fluttering or pounding in your chest, even at rest.
A fast heart rate, especially when combined with low blood pressure, indicates that your body is under significant stress. Your heart may work harder to keep blood flow and oxygen levels up, increasing its demand for oxygen and energy.
Some people experience irregular heart rhythms and skipped heartbeats, leading to sensations like palpitations or a sense of impending doom.
Dizziness
You may feel unsteady or lightheaded, as if you are about to faint, especially with sudden head movements. Some people also experience blurry vision alongside dizziness, which may be linked to brain inflammation.
You might need to sit or lie down, frequently hesitating to avoid falling. Some episodes of dizziness are accompanied by a sensation of the room spinning (vertigo), making it difficult to maintain balance and coordination.
Poor Coordination
The infection can impact fine motor skills—making writing, buttoning clothes, using utensils, typing, handling small objects, and fastening zippers increasingly difficult.
Judging distances or reaching for objects accurately may also become challenging, leading to unintended movements or accidents.
For some individuals, delayed reaction times pose serious safety risks, especially during activities that require quick reflexes, such as driving or operating machinery.
Trouble Walking
Walking patterns often change noticeably during invasive listeriosis. You might notice that your walking becomes unsteady, causing you to stumble, shuffle, or lean on walls or furniture for support.
As muscle weakness and poor coordination worsen, you may walk with a wider stance to stay stable. Turning, stopping, or adjusting direction can feel more difficult, increasing the risk of falls.
Personality Changes
Family and friends might notice you become more irritable, anxious, or withdrawn. You may react differently to situations and show less interest in social interactions or daily activities.
The infection’s impact on the nervous system can also affect decision-making and emotional regulation. You might experience sudden mood swings, struggle to concentrate, or find it harder to process thoughts.
Some individuals display aggressive behaviors, such as increased agitation, impulsivity, or difficulty controlling emotions. These personality changes can be temporary and often improve with proper treatment, but recovery may take time.
