Listeria is a type of bacterial infection caused by Listeria monocytogenes, a hardy bacterium that can survive and even thrive in cold environments such as refrigerators. Listeriosis, the infection caused by this bacterium, can lead to a variety of symptoms—from mild flu-like illness to severe complications such as sepsis, meningitis, or miscarriage.

While Listeria infections are relatively rare, they are particularly dangerous for pregnant individuals, newborns, older adults, and people with weakened immune systems. Approximately 1,600 cases of listeriosis are reported in the United States each year, resulting in around 260 deaths.

Common Symptoms

Symptoms of listeriosis can vary depending on the severity of the infection and the person's overall health. The most common symptoms include:

  • Fever

  • Muscle aches

  • Nausea

  • Diarrhea

  • Headache

  • Stiff neck

  • Confusion or disorientation

  • Loss of balance

  • Convulsions

Pregnant individuals may experience milder symptoms, such as fever and fatigue, but the infection can have devastating consequences for the fetus, including stillbirth, premature labor, or life-threatening infection in newborns.

Older adults and people with weakened immune systems are at greater risk of developing severe symptoms, including neurological complications and bloodstream infections.

Main Causes

Listeriosis is caused by the bacterium Listeria monocytogenes, which is naturally found in the environment, including in soil, water, and certain animals. People typically become infected by consuming foods contaminated with this bacterium.

High-risk foods include:

  • Unpasteurized milk and dairy products (including soft cheeses like brie or feta)

  • Processed or ready-to-eat meats (e.g., deli meats, hot dogs)

  • Raw or smoked seafood

  • Precut fruits and vegetables

  • Undercooked or raw sprouts

Unlike many other foodborne bacteria, Listeria can grow at refrigerator temperatures, making proper food storage critical in preventing infection.

Risk Factors

Certain populations are more vulnerable to developing a Listeria infection:

  • Pregnant people: 10 times more likely to contract listeriosis

  • Adults aged 65 and older

  • People with weakened immune systems: Including those with HIV/AIDS, cancer, organ transplants, or chronic diseases

  • Individuals undergoing chemotherapy or immunosuppressive therapy

  • Frequent consumption of high-risk foods

How Listeria Is Diagnosed

If you suspect you’ve been exposed to contaminated food and are experiencing symptoms, it’s important to seek medical attention promptly.

Diagnosis typically involves:

  • Medical history and symptom review

  • Blood tests: To detect the presence of Listeria monocytogenes

  • Cerebrospinal fluid analysis: Especially in suspected meningitis cases

  • Amniotic fluid testing: For pregnant patients experiencing symptoms

Early diagnosis is critical to reducing the risk of complications and ensuring proper treatment.

Treatment Options

In healthy individuals with mild gastrointestinal symptoms, no treatment may be needed beyond supportive care like hydration and rest.

However, more serious cases of invasive listeriosis require antibiotics, especially if the infection spreads beyond the intestines.

Common antibiotics include:

  • Ampicillin

  • Penicillin

  • Amoxicillin

  • Gentamicin (often combined with ampicillin for synergistic effect)

Hospitalization may be required in severe cases, particularly for pregnant people, newborns, or immunocompromised individuals.

Prevention Tips

Although it's impossible to completely eliminate the risk of Listeria, you can significantly reduce it by following these food safety measures:

Safe Food Handling

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

  • Wash raw fruits and vegetables thoroughly

  • Store food at proper refrigeration temperatures (below 40°F or 4°C)

  • Avoid cross-contamination by using separate cutting boards for raw and cooked foods

Avoid High-Risk Foods (especially for pregnant people and immunocompromised individuals):

  • Unpasteurized dairy products

  • Soft cheeses unless labeled as made with pasteurized milk

  • Prepackaged deli meats and hot dogs (unless reheated to steaming)

  • Refrigerated pâtés or meat spreads

  • Raw sprouts

  • Smoked seafood unless cooked

Kitchen Hygiene

  • Wash hands before and after handling food

  • Sanitize countertops, knives, and cutting boards after preparing raw meat

  • Clean refrigerator spills immediately, especially from meat juices

  • Use perishable food within recommended storage times

Potential Complications

In high-risk individuals, Listeria infections can lead to serious health outcomes:

  • Sepsis: Infection spreads through the bloodstream

  • Meningitis: Inflammation of membranes surrounding the brain and spinal cord

  • Brain abscesses: Rare, but life-threatening

  • Miscarriage or stillbirth: When Listeria crosses the placenta

  • Neonatal listeriosis: Can cause respiratory distress, infections, or death in newborns

Long-term neurological effects may also occur in survivors of Listeria meningitis.

Living With Listeria

For most people, a full recovery is expected with timely treatment. However, complications in vulnerable individuals may require long-term care or rehabilitation.

Key recovery practices include:

  • Strict adherence to prescribed antibiotics

  • Nutritional support and hydration

  • Close follow-up with healthcare providers

  • Neurological monitoring if central nervous system involvement occurred

  • Avoidance of high-risk foods during and after recovery, especially in pregnant patients