Listeriosis is an infection that usually develops after eating food that's been contaminated by bacteria called Listeria monocytogenes, which is commonly known as listeria.
In most people, listeriosis is mild and causes flu-like symptoms or vomiting and diarrhoea (gastroenteritis). Read more about the symptoms of listeriosis.
Symptoms usually pass within three days without the need for treatment.
However, in rare cases, the infection can spread to other parts of your body and cause serious complications, such as meningitis (infection of the membranes surrounding the brain and spinal cord). Doctors describe this as invasive listeriosis.
If this is the case, you'll need to be treated with antibiotics in hospital for several weeks.
Read more about the treating listeriosis.
Where is listeria found?
The listeria bacteria have been found in a range of chilled 'ready-to-eat' foods, including:
- pre-packed sandwiches
- soft cheeses, such as Brie or Camembert or others with a similar rind
- soft blue cheese
- cooked sliced meats
- smoked salmon
The best way to prevent 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.
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.
Types of listeriosis
Most listeria infections are limited to the digestive system and cause mild symptoms. Doctors call this non-invasive listeriosis.
Invasive listeriosis occurs when the infection spreads to the blood or central nervous system, before spreading to the brain. This type of infection can be potentially fatal.
People with weakened immune systems are particularly vulnerable to invasive listeriosis.
- people who are over 60 years old
- pregnant women and their unborn babies
- babies who are less than one month old
- people with a health condition that weakens their immune system, such as HIV/AIDS or diabetes
- people who are receiving medication that weakens their immune system, such as chemotherapy or radiotherapy
Read more about what causes listeriosis.