Listeria: Symptoms and How it Affects Pregnancy

The bacterium Listeria monocytogenes causes listeriosis in humans, a serious disease characterised by fever and muscle aches as well as other gastrointestinal problems.

Symptoms caused by listeria are usually only seen in people over 65 years of age, pregnant women, newborns and people with a weakened immune system.

How does infection occur?

This bacterium can basically be found in food (in most cases of animal origin, as it is transmitted from animals to humans) that is spoiled, poorly processed and/or raw. The infection is invasive, i.e. it can be absorbed by the intestines and distributed through the bloodstream.

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Listeria symptoms and recommendations

On gaining access to the intestines, the bacteria usually cause the following symptoms:

  • Fever
  • Chills
  • Muscle aches
  • Nausea
  • diarrhoea

If it invades the nervous system, symptoms worsen:

  • Headache
  • Stiff neck
  • Confusion or changes in alertness
  • Loss of balance
  • Seizures

One thing that should not be overlooked is that although signs usually appear within a few days of eating contaminated food, they can be delayed for up to 30 days.

What can you do if you contract Listeriosis?

We advise you to seek medical advice if you have eaten food recalled due to a Listeria outbreak and show signs of infection. The same advice also applies to the consumption of food made with raw milk, hot dogs or undercooked deli products.
In case of the following symptoms

  • High fever
  • Severe headache
  • Stiff neck
  • Confusion
  • Sensitivity to light

We strongly recommend that you go to the nearest emergency room, as the above list corresponds to the signs of bacterial meningitis, a life-threatening complication that can be caused by infection with this bacterium.

Listeria in pregnancy: newborns

For pregnant women, the infection is usually mild, but not for babies, who can be devastatingly affected. Since the newborn does not have an effective immune system, the following scenarios can occur:

  • Pre-birth foetal death.
  • Life-threatening infection after birth.
  • Spontaneous miscarriage.
  • Premature birth

Listeria control and prevention

There are a number of control and prevention measures which are outlined below:

  • Keep away from raw food.
  • Heat pre-cooked food correctly.
  • Wash hands properly before handling food.
  • Thoroughly wash vegetables and fruit before eating them (although they do not come from animals, their growth may have been enhanced by faeces or manure containing Listeria).
  • During pregnancy, follow the instructions of specialised medical personnel.



This microorganism can be very dangerous, especially for the extremes of age, foetuses and newborns and immunodeficient, in CALITEC we offer audit services, analysis and quality control.
If you are interested in hiring any of them to demonstrate that the products of your brand are safe to ingest, click on this link and fill in the form, we will contact you as soon as possible.



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