What Is Listeria and How It Can Affect Your Health

Listeria is a bacterial infection that causes foodborne illness and can lead to a wide range of symptoms—from mild flu-like effects to serious complications. It is particularly dangerous for vulnerable groups such as pregnant women, newborns, older adults, and individuals with weakened immune systems.

The most common way people become infected is by consuming contaminated food. If left untreated, Listeria infection can lead to serious health outcomes. Fortunately, treatment options and preventive measures are available to manage and reduce the risks of listeriosis.

Listeria Symptoms

Listeria infections can result in a variety of symptoms, which may differ in intensity depending on the person’s age, immune system, and overall health. Common symptoms include:

• Fever

• Muscle aches

• Nausea

• Diarrhea

• Headache

• Stiff neck

• Confusion or changes in alertness

• Loss of balance

• Convulsions

• Flu-like symptoms

in pregnant individuals: Symptoms may be mild, like a fever or flu-like effects, but the consequences can be serious, including miscarriage, stillbirth, premature birth, or severe infection in the newborn.

in older adults and immunocompromised individuals: Symptoms may progress quickly and become more severe. If Listeria is suspected, immediate medical attention is necessary.

What Causes Listeria?

Listeria is caused by the bacterium Listeria monocytogenes, which can be found in soil, water, and some animals. Unlike many other bacteria, L. monocytogenes can survive and even multiply in cold environments like refrigerators.

common food sources of contamination include:

• Unpasteurized dairy products

• Contaminated vegetables

• Raw or pre-packaged fruits

• Processed meats such as deli meat and hot dogs

• Raw or smoked fish

Because the bacteria can grow at refrigeration temperatures, storing contaminated foods for a long time can increase the risk of infection.

Risk Factors

Certain individuals are at greater risk for Listeria infection, including:

• Pregnant individuals

• People over the age of 65

• Those with weakened immune systems due to conditions like HIV/AIDS or cancer

• Individuals undergoing medical treatments such as chemotherapy or organ transplants

• Anyone who frequently consumes high-risk foods

in pregnant individuals: Due to immune system changes during pregnancy, they are significantly more susceptible to Listeria and may face serious complications.

How Is Listeria Diagnosed?

If you’re experiencing symptoms and suspect exposure to contaminated food, consult a healthcare provider promptly. Diagnosis involves discussing your symptoms and risk factors, followed by laboratory tests.

common diagnostic procedures:

• Blood samples

• Cerebrospinal fluid

• Amniotic fluid (for pregnant individuals)

These tests help detect the presence of Listeria monocytogenes in bodily fluids or tissues and determine the appropriate treatment.

Treatments for Listeria

Many cases of intestinal Listeria resolve without antibiotics. If you experience diarrhea, staying hydrated is essential.

for invasive listeriosis: When the infection spreads beyond the intestines, antibiotic treatment becomes necessary. The choice of antibiotics depends on the infection’s severity and the patient's health condition.

commonly used antibiotics include:

• Penicillin (e.g., Zosyn)

• Ampicillin (e.g., Omnipen)

• Amoxicillin (e.g., Moxatag)

These may be used alone or in combination with gentamicin, especially in severe cases.

in serious infections: Hospitalization may be needed to administer intravenous antibiotics and provide supportive care. Pregnant individuals diagnosed with listeriosis may also require hospitalization to reduce risks for themselves and the baby.

How To Prevent Listeria

Although Listeria infection can’t always be avoided, several measures can reduce the risk significantly.

practice safe food handling

• Cook meat, poultry, and seafood to safe internal temperatures

• Wash fruits and vegetables thoroughly before eating

• Avoid cross-contamination between raw and cooked foods

• Refrigerate perishable items promptly and consume them within recommended timeframes

avoid high-risk foods

• Avoid unpasteurized milk, yogurt, and soft cheeses

• Avoid raw or undercooked produce like sprouts and melons

• Be cautious with ready-to-eat items such as deli salads, lunch meats, and hot dogs—heat them thoroughly before eating

• If you are pregnant or immunocompromised, consult your doctor about which foods are safe

maintain good hygiene

• Wash hands thoroughly with soap and water before handling food, after handling raw meat, and after using the bathroom

• Clean cutting boards, knives, and kitchen surfaces after each use

• Only eat from clean plates and with clean utensils

• Immediately clean spills in the fridge, especially those from meat or seafood

Complications

Listeriosis can cause serious complications, particularly in pregnant people, newborns, the elderly, and those with weakened immune systems.

pregnancy complications: Listeria can cross the placenta, causing miscarriage, stillbirth, premature birth, or newborn infection.

sepsis: When Listeria spreads through the bloodstream, it can lead to sepsis, a life-threatening response to infection that affects multiple organs.

meningitis: This infection can reach the brain and spinal cord, resulting in meningitis—an inflammation of protective membranes that can cause neurological symptoms.

brain abscess: In rare cases, Listeria can cause brain abscesses, which are pockets of infection within brain tissue.

A Quick Review

Listeria is a dangerous foodborne bacterial infection, especially for vulnerable groups such as pregnant individuals, infants, the elderly, and those with weakened immune systems. It can be prevented through safe food practices, avoiding high-risk foods, and maintaining hygiene.

If you suspect Listeria exposure or experience symptoms, seek medical help immediately. Early diagnosis and proper treatment are essential to managing the infection and preventing serious complications.