Listeria Symptoms

Listeria monocytogenes is a gram-positive bacterium that can invade your body and quickly reproduce in your system causing Listeriosis, a type of food poisoning.

In the U.S., an estimated 2,500 severe cases of Listeriosis are reported, with the food poisoning being especially dangerous to children, infants, pregnant women, and the elderly, according to the Mayo Clinic. According to the CDC, some 260 people die each year due to related food poisoning.

Many of the most severe cases are associated with pregnant women since Listeriosis can cause women to miscarry, have premature deliveries, cause stillbirths, or can infect the child if the mother has an infection present at any time during her pregnancy.


When an otherwise healthy adult or child becomes infected with Listeria monocytogenes, they typically are not at risk for a serious infection. MedicineNet says that most people who are infected present few or no symptoms.

What Is Listeria?

Listeria is a bacterium commonly found in water and soil. It is associated with manure, so it often contaminates vegetables that both people and animals eat; this means meats, dairy products, eggs, and vegetables all carry a risk of exposure

It contaminates foods typically due to improper preparations. It is often found when foods are not cooked, undercooked or when liquids, such as milk, are not pasteurized or otherwise treated.

The CDC notes that some “ready-to-eat” foods such as deli meat and hot dogs can become contaminated even if properly cooked because they may come into contact with raw food products or have other exposures before they are packaged. Other health sources note the same exposure risks to soft cheeses.

Foods that come in contact with animal and/or human waste also provide a home for the bacteria.

The bacteria can survive being refrigerated and even being frozen, so the CDC and the Mayo Clinic recommend those at higher risk for a serious infection to avoid eating the foods associated with outbreaks or commonly linked to Listeria.


The symptoms of a Listeria infection may be mild at first and can take some time grow in severity and present as dangerous. Symptoms can occur as soon as two days after eating food that is contaminated, or they can take as long as two months for the infection to be severe enough to cause symptoms.

Initial symptoms of Listeriosis include:

  • Diarrhea,
  • Fever,
  • Nausea and upset stomach,
  • Vomiting,
  • And other flu-like symptoms.

Listeriosis becomes a significant risk if it spreads to the nervous system. If it has spread, you will likely experience:

  • Constant headaches,
  • Stiff and sore neck,
  • Loss of balance,
  • Bouts of confusion,
  • A change to general alertness,
  • And potentially convulsions.

Listeriosis presents differently in each case and depends on your body, so it may manifest different in you from others that get sick from the same infection point. If you know someone who gets sick with these symptoms and you may have eaten an at-risk food with them, it is recommended to consult with your doctor.

Seeing Your Doctor

If you have any of the symptoms described above and you have eaten food that’s been recalled because of a Listeria outbreak, you should contact your doctor.

You should also contact your doctor if these symptoms follow consumption of potentially contaminated foods, including processed foods, such as undercooked meats and hotdogs or foods made with unpasteurized milk.

Seek emergency care if you are suffering any of the symptoms associated with Listeria infecting your nervous system as these can be life-threatening. A common side effect or complication of a Listeria infection that reaches the nervous system is bacterial meningitis.

Bacterial meningitis can cause serious bodily harm, such as brain damage, hearing loss and memory impairments. It is especially dangerous to newborns – and typically linked to Listeria infections in newborn cases – so it must be taken very seriously, says the CDC.


Listeriosis is diagnosed by your doctor taking your medical history, including recent possible exposure, and a physical exam. If symptoms are present, your doctor will take a blood or stool sample to test.

The CDC recommends blood be used for Listeriosis test since it believes that stool samples are “of limited use” and may not provide accurate detection. Patients may also undergo a spinal fluid test to confirm a diagnosis, but this is rare since blood test can usually detect the infection.

If there is a concern during pregnancy, doctors can test the amniotic fluid or placenta.

Cultures usually take 1 to 2 days for bacteria growth, so test are fairly quick. However, if you exhibit signs of an infection your doctor may take steps to treat you even if your results come back negative.

Listeria and Pregnancy

Most medical professionals will tell you to be extra careful of the foods you eat when pregnant because, while somewhat rare, pregnant women are more susceptible to Listeriosis.

CDC estimates find that about 17% Listeriosis cases in the U.S. are of pregnant women, making them roughly 20-times more likely to develop the infection than the average healthy adult.

Pregnant women are most susceptible during their third trimester because their immune system is slightly suppressed – though because of the incubation period this means the infection can initially happen during the second trimester and present severely during the third.

While health risks are not typically severe for the mother, they can endanger the child.

Listeriosis infection while pregnant increases the risks for:

  • Miscarriages;
  • Neonatal death;
  • Premature deliveries;
  • And infections present in the newborn.

Roughly 22% of perinatal Listeriosis infections result in the death of the child.

Early detection and treatment can help prevent a fetus from becoming infected or can limit the risks of a fetus. Thankfully, not all newborns of infected mothers suffer from Listeriosis at birth.

Prevention and Treatment

Listeriosis is typically only treated for those at high risk, such as pregnant women, the elderly, and newborns; otherwise-healthy adults are typically not treated as symptoms go away within a few days or weeks, according to WebMD.

High-risk populations are treated with antibiotics, especially pregnant women since antibiotics can prevent the transfer of the bacteria from mother to child. Newborns with Listeriosis are given the same antibiotics as adults, allowing for continued treatment from time in the womb to the months following birth.

Keeping Yourself Safe

There are a variety of steps you can take to keep yourself safe from Listeria. The best prevention comes from the smart handling and storage of your food. This means that you should shop near your home and put groceries up as soon as possible. When shopping, bag raw meats, poultry, and dish to prevent any liquids from touching other foods.

When cooking, always wash your fruits and vegetables with running water. Always wash your hands too. Prepare your vegetables and other items separately from raw meat – don’t share cutting boards or knives! You should also wash your cutting boards and knives very carefully after use.

Your foods should be cooked and served properly, heating meats to the proper temperatures and not allowing them cool before being served. Leftovers should be thoroughly re-cooked as well.

Listeria can grow in your refrigerator, so promptly clean up and disinfect any spills that happen in your fridge or freezer.

If you are an at-risk or high-risk population, the medical professionals have specific recommendations for you:

  • Avoid soft cheeses and “Mexican” style cheeses if the packaging doesn’t specifically state that it was pasteurized.
  • If you want to eat a hotdog, make sure it is cooked until “steaming hot” and keep all fluids in its packaging away from other foods, says the Mayo Clinic.
  • You shouldn’t eat any refrigerated smoked seafood, period. It is a significant risk. A great rule of thumb from WebMD is: “when in doubt, throw it out!”

Recent Outbreaks and Detection

The CDC has noted one major Listeria outbreak for each of the last three years. The 2011 risk was associated with cantaloupes while both the 2012 and 2013 outbreaks were caused by cheeses.

Between May and July of 2013, six people were infected with a strain of Listeria traced back to the Crave Brothers Farmstead cheeses. Infections took place in five states: Illinois, Indiana, Minnesota, Ohio, and Texas. One of the infected individuals in Minnesota died as a result, while another individual had a miscarriage related to Listeriosis.

On July 3, the Waterloo, Wisconsin Crave Brothers company issued a voluntary recall of its Les Frères, Petit Frère, and Petit Frère with Truffles cheeses that were made July 1 or earlier because of a believed Listeria contamination.

The Food and Drug Administration followed up with testing and inspection, finding a sample of the Petit Frère with Truffles cheese to be contaminated with the same Listeria strain associated with the outbreak. The company sells its cheeses through national distributors, retailers, food service chains, and mail order catalogs.

The FDA and CDC issued health warnings associated with the outbreak, but also cautioned high-risk populations to be wary of these foods even outside of an outbreak. The strain found in contaminated samples is associated with other cases each year.


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