Listeriosis is an infection that usually develops after eating food contaminated by listeria bacteria.

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, severe headache and tremors.

Read more about the symptoms of listeriosis.

Where is listeria found?

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

The bacteria may also be passed on through contact with the stools of infected animals or human carriers.

Read more about what causes listeriosis.

Seeking medical help

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

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

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

Mild cases of listeriosis usually don't 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 treating listeriosis.

Preventing listeriosis

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

  • not use food past its "use by" date
  • follow storage instructions on food labels
  • make sure that the temperature of your fridge is 0C to 5C
  • cook food thoroughly

If you're in a high risk group for listeriosis – for example, if you're pregnant or you have a weakened immune system, 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 65 years of age 
  • pregnant women and their unborn babies
  • babies less than one month old
  • people with a weakened immune system, such as those with HIV/AIDS or receiving 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.

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