Listeriosis: Everything You Need to Know

Listeriosis is a rare infection that can lead to severe complications. We'll tell you everything that is known about it.
Listeriosis: Everything You Need to Know

Last update: 14 February, 2023

Listeriosis is a disease that occurs through infection by the bacteria Listeria monocytogenes. According to the World Health Organization (WHO), an average of 0.1 to 10 cases per million inhabitants are reported each year. Therefore, it’s a very rare disease which is also prone to complications.

Although there may be isolated cases, most of the episodes occur in the form of flare-ups. This means when the disease arises in a limited group of people and in a specific geographical area, and shares the same source or origin. There are two types of the disease: invasive and non-invasive. We will talk about this below.

Symptoms of listeriosis

Fever in listeriosis.
The symptoms of listeriosis can be very diverse depending on the severity of the disease. Fever is a common manifestation in most cases.

Listeriosis is a disease that tends to get complicated very easily. The Food and Drug Administration (FDA) warns that up to 94% of infected people require hospitalization. Of these cases, between 20% and 30% end in death. However, it all depends on the characteristics the disease occurs with.

Indeed, mild cases are usually classified as non-invasive listeriosis and mainly affect healthy adults. It is also known in some contexts as febrile listerial gastroenteritis and is distinguished by the following symptoms:

  • Headaches
  • Diarrhea
  • Muscle pain
  • Fever

The incubation period is short, and generally doesn’t generate complications beyond those indicated. The most serious cases are described as invasive listeriosis and affect risk groups such as pregnant women, infants or young children, patients with compromised immune systems (cancer or HIV patients) and older adults. The statistics presented by the FDA correspond to these cases.

Episodes of this type have a longer incubation period. It can be several weeks and even months. By then, the bacteria lodge and multiply in the liver before being released into the bloodstream. When this happens, patients develop the following symptoms:

  • Muscle pain
  • Fever
  • Meningitis
  • Encephalitis
  • Septicemia

According to the researchers, the infection is on average 20 times more common in pregnant women than in other population groups. Although it doesn’t usually cause problems for the mother, it can be life-threatening for the fetus. It is for this reason that most cases require hospitalization.

Transmission of listeriosis

Listeriosis is contracted by infection with the bacterium L. monocytogenes. This microorganism has a very varied habitat and supports extreme temperatures (compared to other similar ones). For example, it can inhabit water, soil, plants, and animals. In addition, it can tolerate acidic, salty conditions and those with very low humidity concentrations.

At the same time, it resists low temperatures very well (it can even continue to reproduce under these conditions). This tells us that the bacteria can survive even in properly refrigerated food. That said, the infection is spread primarily by eating food with the bacteria.

Other ways you can get listeria is by handling contaminated food (for example, pet food) and by touching surfaces or utensils with the bacteria. Once it is in your hands, it moves inside you when you unexpectedly touch the mucous membranes (eyes, nose, ears and mouth). Babies become infected through their mother’s placenta.

Although in theory any food can be infected with the bacteria, there are some that are more likely to do so than others. The Centers for Disease Control and Prevention (CDC) warn of the following groups:

  • Cheeses made with unpasteurized milk
  • Raw foods (alfalfa, radish, some types of beans, and so on)
  • Melons
  • Sausage products (hams, sausages and others)
  • Fast food (hamburgers and hot dogs)
  • Smoked fish
  • Unpasteurized raw milk
  • Pate

Proper cooking of food, pasteurization, and sanitizing agents are usually effective in getting rid of the bacteria. Still, contamination can occur after performing these procedures.

Diagnosis of listeriosis

The diagnostic process for listeriosis begins with an evaluation of the patient’s symptoms. The specialist will suspect a possible bacterial infection based on these, as well as reviewing the person’s history of habits. In this way, he will proceed to make a bacterial culture through a sample of blood, cerebrospinal fluid, placenta, and others.

Blood tests are widely used for differential diagnoses. Since the symptoms can easily be confused with other types of infections or diseases, the mediation of a confirmatory culture is very important. Stool and urine tests can also be done as a supplement.

If an outbreak of listeria has been reported related to certain food groups or brands that you include in your diet, you should suspend their consumption and go to a specialist to carry out tests for elimination. Try to act quickly especially if you’re part of risk groups.

Treatment options

Intravenous treatment for listeriosis.
Since most people with listeriosis require hospitalization, the use of intravenous antibiotics is an essential part of therapy.

As with other types of bacterial infections, most patients are treated with antibiotics. The dosage and use of these varies according to the severity of the symptoms. Its use may even be skipped if the patient is stable, has a strong immune system, and is a healthy adult.

In risk groups, treatment based on these drugs isn’t optional. You must act promptly, as it isn’t uncommon for the infection to worsen unexpectedly. Specific drugs may also be prescribed to counter acute symptoms.

Keep in mind at this point that, even though listeriosis is a rare disease, you should include the respective prevention methods in your routine. These are no different from prevention methods to protect you from other infections. We highlight the following:

  • Avoid touching the mucous membranes with your hands.
  • Wash your hands frequently with soap for at least 20 seconds.
  • Wash fruits and vegetables.
  • Make sure you respect food cooking.
  • Avoid eating raw dishes.
  • Reduce the consumption of sausages.
  • Maintain cleanliness standards in your kitchen and throughout your home.
  • Keep your refrigerator clean.
  • Sanitize kitchen utensils regularly.
  • Stay tuned for outbreak bulletins being reported in your community.

If you have been diagnosed with listeriosis, in addition to following the treatment, you should rest to speed up your recovery. Try to monitor the symptoms to let the specialist know if there are any complications.

  • Janakiraman, V. Listeriosis in pregnancy: diagnosis, treatment, and prevention. Reviews in Obstetrics and Gynecology. 2008; 1(4): 179.

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