Listeria infection, also known as listeriosis, is caused by the bacteria Listeria monocytogenes. These bacteria are most commonly found in foods that include:

  • unpasteurized dairy products
  • certain deli meats
  • melons
  • raw vegetables

Listeriosis isn’t serious in most people. Some people may never even experience symptoms of the infection, and complications are rare. For some people, though, this infection can be life-threatening.

Treatment depends on how severe the infection is and your overall health. Proper food safety can help prevent and reduce your risk for developing listeriosis.

The most common symptoms for listeriosis include:

  • fever
  • nausea
  • diarrhea
  • muscle aches

For a lot of people, the symptoms may be so mild that the infection stays undetected.

Symptoms can begin within one to three days after eating contaminated food. The mildest symptom is a flu-like illness with diarrhea and fever. Some people don’t experience the first symptoms until days or weeks after exposure.

Symptoms will last until the infection is gone. For some people diagnosed with listeria, treatment with antibiotics is often recommended. There may be a high risk of complications, especially within the nervous system, heart, and blood stream. This infection is especially risky in pregnant women, people age 65 and older, and people with a weakened immune system.

In some cases, listeriosis can spread outside the intestines. This more advanced infection, known as invasive listeriosis, causes more severe symptoms. These include:

  • headache
  • confusion
  • stiff neck
  • changes in alertness
  • loss of balance or difficulty walking
  • convulsions or seizures

Complications include bacterial meningitis, an infection of the valves of the heart (endocarditis), and sepsis.

You will need a stay in the hospital to treat a more serious infection as it may be life-threatening.

If you’re pregnant, you may not experience many symptoms, or the symptoms may be so mild you don’t realize you have the infection. Listeriosis in pregnant women may lead to miscarriage or stillbirth. In cases where the baby survives, they may develop a serious infection of the brain or blood that requires further hospitalization and treatment with antibiotics right after birth.

Listeriosis develops after you come into contact with the bacteria Listeria monocytogenes. Most commonly, a person contracts listeria after eating contaminated food. A newborn can also get it from their mother.

Listeria bacteria live in soil, water, and animal feces. They can also live on food, food production equipment, and in cold food storage. Listeriosis is commonly spread by:

  • processed meats, including deli meat, hot dogs, meat spreads, and refrigerated smoked seafood
  • unpasteurized dairy products, including soft cheeses and milk
  • some processed dairy products, including ice cream
  • raw vegetables and fruit

Listeria bacteria are not killed in the cold environments of refrigerators and freezers. They don’t grow as quickly in cold environments, but they can survive freezing temperatures. These bacteria are more likely to be destroyed by heat. Heating processed foods, like hot dogs, to 165°F (73.8°C) will kill the bacteria.

Healthy people will rarely become ill because of Listeria. People with compromised immune systems may experience more severe symptoms. You’re more likely to develop an advanced infection or complications from listeriosis if you:

  • are pregnant
  • are over 65
  • are taking immune suppressants, such as prednisone or other medications prescribed to treat autoimmune diseases like rheumatoid arthritis
  • are on medications to prevent organ transplant rejection
  • have HIV or AIDS
  • have diabetes
  • have cancer or are undergoing chemotherapy treatments
  • have kidney disease or are on dialysis
  • have alcoholism or liver disease

If you ate a food that has been recalled, don’t assume you should see your doctor. Instead, monitor yourself and pay close attention to symptoms of an infection, like fever over 100.6°F (38°C) or flu-like symptoms.

If you start feeling ill or experiencing symptoms of listeriosis, make an appointment with your doctor. If you have a compromised immune system, it’s important you check in with your doctor. Let them know you believe you ate food that was infected with listeria. If possible, provide details about the food’s recall and explain all your symptoms.

Your doctor will likely use a blood test to diagnose listeriosis. Spinal fluid tests are also sometimes used. Prompt treatment with an antibiotic can reduce the symptoms of the infection and prevent complications.

Treatment for listeriosis depends on how severe your symptoms are and your overall health.

If your symptoms are mild and you are otherwise in good health, treatment may not be necessary. Instead, your doctor may instruct you to stay home and care for yourself with close follow-up. Home treatment for listeriosis is similar to treatment for any foodborne illness.

Home remedies

To treat a mild infection at home:

  • Stay hydrated. Drink water and clear liquids if you’re experiencing vomiting or diarrhea.
  • Switch between acetaminophen (Tylenol) and nonsteroidal anti-inflammatory drugs (NSAIDs) to reduce any fever or muscle aches.
  • Try the BRAT diet. While your intestines return to normal, eating foods that are easy to process can help. These include bananas, rice, applesauce, and toast. Avoid spicy foods, dairy, alcohol, or fatty foods like meat.

Medical treatments

If your symptoms are severe, you’re feeling worse, or you’re showing symptoms of an advanced infection, your doctor will usually prescribe antibiotics. You will likely need to stay in the hospital and be treated with IV medications. Antibiotics through an IV can help eliminate the infection, and the hospital staff can watch for complications.

Treatment in pregnancy

If you’re pregnant and have listeriosis, your doctor will want to begin treatment with an antibiotic. They’ll also monitor your baby for signs of distress. Newborn babies with an infection will receive antibiotics as soon as they’re born.

Outlook | Outlook

Recovery from a mild infection may be quick. You should feel back to normal within three to five days.

If you have a more advanced infection, recovery depends on the severity of the infection. If your infection becomes invasive, recovery may take up to six weeks. You may also need to stay in the hospital during part of your recovery so you can have IV antibiotics and fluids.

An infant born with the infection may be on antibiotics for several weeks while their body fights the infection. This will likely require the newborn to remain hospitalized.

Food safety measures are the best way to prevent listeria:

  • Clean your hands, counters, and appliances. Reduce the possibility of cross-contamination by washing your hands before and after cooking, cleaning produce, or unloading groceries.
  • Scrub produce thoroughly. Under running water, scrub all fruit and vegetables with a produce brush. Do this even if you plan to peel the fruit or vegetable.
  • Cook foods well. Kill bacteria by fully cooking meats. Use a meat thermometer to ensure you’ve reached recommended temperatures.
  • Avoid possible sources of infection if you’re pregnant. During the time you’re expecting, skip foods that could be infected, like unpasteurized cheeses, deli and processed meats, or smoked fish.
  • Clean your fridge regularly. Wash shelves, drawers, and handles with warm water and soap regularly to kill bacteria.
  • Keep temperatures cold enough. Listeria bacteria don’t die in cold temps, but a properly cooled fridge can slow bacteria growth. Invest in an appliance thermometer and maintain a refrigerator temperature at or below 40°F (4.4°C). The freezer should be at or below 0°F (-17.8°C).