Listeria is a foodborne bacteria which can make you sick. Infection with listeria bacteria is called listeriosis. In healthy adults and children listeria usually causes few or no symptoms, but some people are more at risk of severe disease.
Who is at risk of severe disease?
People who are more at risk include:
- pregnant women and their unborn babies
- newborn babies
- people with weakened immune systems (including cancer patients, diabetics, people taking immunosuppressive treatments, people with liver or kidney disease
- frail older people. 
Listeriosis is particularly dangerous for pregnant women. It can cause miscarriage, premature labour or stillbirth, and can cause infection in their baby.
Listeria and food safety
Food safety procedures aim to prevent listeria getting into foods we eat. However some foods are more likely to be contaminated and so people who are at risk of severe disease should not eat them.
Foods that are unsafe for people at risk of severe infection include:
- uncooked, smoked or ready-to-eat fish or seafood, including oysters, prawns, smoked ready-to-eat fish, sashimi or sushi
- paté, hummus-based dips and spreads
- cold pre-cooked chicken
- ham and all other chilled pre-cooked meat products including chicken, salami and other fermented or dried sausages*
- pre-prepared or stored salads (including fruit salads) and coleslaws
- raw (unpasteurised) milk and any food that contains unpasteurised milk*
- soft-serve ice creams
- soft, semi-soft or surface-ripened soft cheese (eg, brie, camembert, feta, ricotta, roquefort).*
* Note that the foods on this list are safe to eat if heated thoroughly to steaming hot (ie, above 72°C) where appropriate.
Safer food choices
For comprehensive information on food safety for people with low immunity refer to the Ministry for Primary Industries guide: Pullout guide to food safety with low immunity (PDF, 784 KB).
- While this group is not strictly defined, a frail older person can be considered as a person over 65 who is in a vulnerable state of health that puts them at greater risk of further deterioration, ill-health or illness. More information about frailty in older people is available in Food and Nutrition Guidelines for Healthy Older People: A background paper.
If you’ve eaten contaminated food the symptoms can take a few days to a few weeks to show up.
- mild fever
- aches and pains
- feeling sick or nauseous
- vomiting or diarrhoea
- stomach cramps.
Some people get very sick with listeriosis. It can cause fever, meningitis, delirium and coma. In some cases, it can be fatal.
If you think you might have listeriosis, see your doctor.
If you or anyone in your household is in the high risk group, it is important to take a few simple precautions.
- Follow good food hygiene practices, such as washing and drying hands before preparing food and after handling or preparing raw foods.
- Eat freshly cooked or freshly prepared foods.
- Wash raw fruit and vegetables very well before eating.
- Cook foods thoroughly to kill any listeria bacteria.
- Refrigerate leftovers immediately and do not keep for more than 2 days. Reheat to steaming hot (over 72°C) before eating.
- Avoid eating high-risk foods.
Listeria is one of the few food bacteria that will grow on food even if it’s in the fridge, and it can even withstand freezing. It’s important that any perishable food stored in the fridge is used within 2 days.
The Ministry for Primary Industries has more information on safer foods choices in their Pullout guide to food safety with low immunity (PDF, 784 KB).