Listeriosis is an infection that usually develops after eating food contaminated by bacteria called Listeria monocytogenes, commonly known as listeria.

In most people, listeriosis is mild and causes symptoms including a high temperature (fever), vomiting and diarrhoea. These symptoms usually pass within three days without the need for treatment.

However, in rare cases, the infection can be more severe and spread to other parts of your body, causing serious complications, such as meningitis. Common signs of severe listeriosis include a stiff neck, a severe headache and tremors.

Pregnant women are at an increased risk of developing listeriosis.

Read more about the symptoms of listeriosis.

Where is listeria found?

The listeria bacteria have been found in a range of chilled ‘ready-to-eat’ foods, including:

  • pre-packed sandwiches
  • pâté
  • butter
  • soft cheeses, such as Brie or Camembert or others with a similar rind
  • soft blue cheese
  • cooked sliced meats
  • smoked salmon

Read more about what causes listeriosis.

Seeking medical help

If you are pregnant and show signs of listeriosis, or if you have a young child who shows signs of the illness, you should seek immediate medical advice.

If you are not pregnant and are an otherwise healthy adult, you should seek medical help if your symptoms are severe.

Listeriosis is usually diagnosed with a blood test. If it is thought that the infection has spread to the nervous system, further tests may include a MRI scan and a lumbar puncture.

Mild cases of listeriosis usually do not need treatment. However, if the infection has spread to the nervous system, you'll need to be treated with antibiotics in hospital for several weeks.

Read more about the treating listeriosis.

Preventing listeriosis

The best way to reduce your chances of developing listeriosis is to ensure that you always practise good food hygiene. For example, you should:

  • not use food that's past its ‘use by’ date
  • follow storage instructions on food labels
  • make sure that the temperature of your fridge is between 0ºC and 5ºC
  • cook food thoroughly

If you're in a high risk group for listeriosis – for example, if you're pregnant or if you have a weakened immune system, you should avoid eating some foods, such as soft mould-ripened cheese or pâté.

Read more about preventing listeriosis.

'At-risk' groups

Some people are particularly vulnerable to severe listeriosis. 
This includes:

  • people over 60 years of age 
  • pregnant women and their unborn babies
  • babies who are less than one month old
  • people with a weakened immune system, such as those with HIV/AIDS or those receiving some types of medication such as chemotherapy

Listeriosis and pregnancy

Pregnant women are at particular risk of developing listeriosis. This is because the body's natural defences against the listeria bacteria are weaker during pregnancy.

Pregnant women are almost 20 times more likely to develop listeriosis compared with the rest of the population.

A listeria infection in pregnancy doesn't usually pose a serious threat to the mother’s health. However, it can cause pregnancy and birth complications, and can result in miscarriage. An estimated 22% of pregnancy-related cases of listeriosis will result in the death of the baby.

For more information, see:

Eating well during pregnancy

A GP offers advice on how to eat a healthy, balanced diet during your pregnancy. She explains how to prepare certain foods, such as meats and eggs, and offers advice about which foods to eat with caution, and which to avoid completely.

Media last reviewed: 05/04/2013

Next review due: 05/04/2015

How common is listeriosis?

In 2011, there were an estimated 147 cases of listeriosis in England and Wales, 27 of which were in pregnant women.

How to prepare and cook food safely

How to prepare and cook food correctly to reduce the risk of food poisoning, including E. coli

Foods to avoid if you're over 65

Find out why over-65s are at higher risk of food poisoning and what foods are risky

Page last reviewed: 17/01/2013

Next review due: 17/01/2015