Ten Facts About Listeria

Listeria bacteria usually affects vulnerable people who contract food poisoning by eating food contaminated with the species Listeria monocytogenes.

Until 1992 there were 10 known species of Listeria bacteria, and although this number rose to 15 as of 2014, it’s still quite rare to catch an infection.

Read on for 10 facts about Listeria, including what symptoms you can expect if you’re unfortunate enough to contract Listeriosis and how to prevent further infections spreading…


1. Listeria are rod shaped bacteria which were first discovered in the 1920s.  When causing an infection its incubation period can vary between 3 and 70 days.  The incubation period is the length of time between first being exposed to the bacteria and showing symptoms of infection.


2. Although Listeriosis is formally diagnosed through a blood test, common symptoms include a stiff neck, headaches, fever, vomiting and diarrhoea which can last around 3 days.  Milder cases can be treated with paracetamol, ibuprofen and staying well hydrated.


3. In rare cases the infection can be much more severe and spread to other parts of the body potentially leading to sepsis and meningitis.  


4. As with most pathogens, the people most at risk at those with weakened immune systems, people with underlying health issues, the very old and very young and pregnant women.


5. Pregnant women are 10 times more likely than other at-risk groups to contract a Listeria infection so it’s always advised to avoid high risk foods.


6. Since the 1990s high risk foods have included ready to eat chilled foods such as pre-packed sandwiches, pate, butter, cooked sliced meats and smoked salmon.


7. In more recent years outbreaks have been traced back to soft cheeses, celery, sprouts, cantaloupe, raw or unpasteurised milk and ice cream.


8. As Listeria can be found in food production environments, food can be contaminated after cooking but before packaging, slicing or handling in the home so practicing good hygiene is extremely important.


9. Storing food safely helps to reduce the risk of infection.  Ensure you don’t eat food past its “Use By” date, keep your fridge between 0C and 5C and keep uncooked meats, poultry, and seafood separate from vegetables, fruits, cooked foods, and ready-to-eat foods.


10. When cooking food like meat, poultry or seafood, make sure to prepare on clean surfaces with clean equipment and ensure that the centre of your food is piping hot throughout or up to 175C at the thickest part.  Always make sure you wash your hands before and after handling food.


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