Food safety: Avoiding listeria - HE9007

What is listeria?

Listeria is a common bacterium, which can cause a potentially serious illness called listeriosis. Listeriosis is a food-borne infection that results from eating contaminated food.

How do you get listeriosis?

Listeria can be found on plants, in soil, in water, and in animal faeces. It can be found on raw food and can also contaminate prepared food. Chilled or prepared ready-to-eat products and foods, processed meats, soft cheese, and raw food are often linked to outbreaks of listeria.

Who is at risk of becoming very unwell with listeriosis?

In healthy adults and children, listeria usually causes few or no symptoms, but the following people are at more risk of severe illness and complications:

• pregnant women and their unborn babies
• newborn babies
• people with weakened immune systems (includes people who have cancer, diabetes, liver or kidney disease or are taking immunosuppressive treatments)
• older people, usually aged over 65.

Illness: Symptoms and timeframes

You may have no symptoms at all or you may become ill with:

• fever
• muscle aches
• nausea or vomiting
• diarrhoea
• headache.

Listeriosis symptoms appear within 3 days to 5 weeks (usually 3 weeks) after becoming infected. Symptoms usually last for a few days.

In a small number of cases, these symptoms can progress to more severe forms of the illness, such as meningitis and blood poisoning.

Listeriosis can be very serious during pregnancy. It can cause miscarriage, premature labour, or stillbirth and can cause severe infection in the newborn baby. If you think you might have listeriosis, see your doctor immediately.

If you have symptoms

• If you are concerned you or someone you are caring for might have listeriosis, see your usual GP, hauora or healthcare provider, or if very unwell go to the emergency department. They can do blood tests, and other tests to confirm if you have it.
• Take medicines if your doctor prescribes them. If you are pregnant, antibiotics can often prevent infection of your unborn pēpi or newborn.
• Drink plenty of water while you have diarrhoea or vomiting.
• Go back to your GP, hauora or healthcare provider if your symptoms have not gone away after 7 days, you have a fever or bloody diarrhoea.
• Stay away from school, early learning services or work until 48 hours (2 days) after the symptoms have gone.
• Do not go swimming in a pool or spa pool or share bathwater if you have diarrhoea. You need to wait at least 2 weeks after you last had diarrhoea.
• Follow the advice of your doctor or local public health service.

Listeria is a notifiable disease - this means your GP, hauora or healthcare provider will inform your local public health service if you become infected. The public health service may contact you to try and find out how you were infected and if your illness is connected with a food that has been purchased and eaten. This helps to prevent other people from getting listeriosis.

Preventing listeriosis

Most listeria infections come from eating or drinking food that has high levels of the foodborne bacterium Listeria. Some foods (listed below) are more likely than others to become contaminated with Listeria, so people who are at risk of severe illness and complications should not eat them.

Higher-risk foods that are unsafe for people who are at more risk of severe illness and complications:

• ready-to-eat meat products (like deli meats and pâtés)
• smoked seafood (especially cold smoked fish)
• soft cheeses (like brie and camembert)
• uncooked paneer cheese
• unpasteurised dairy products (like raw milk and cheese)
• soft serve ice-cream
• melons
• pre-prepared or pre-packaged fruit salads
• leafy greens and bagged salad (like mesclun and spinach)
• uncooked sprouts (like alfalfa and mung beans) and enoki mushrooms
• uncooked frozen vegetables
• some refrigerated foods with a long shelf life
• pre-prepared sandwiches and salads.

For a more comprehensive list of higher-risk foods and safer substitutes see the following links.

• During pregnancy: Food and pregnancy | NZ Government
• For people with low immunity: Food for people with low immunity | NZ Government

   

Safety with food 

Unlike other harmful bacteria, Listeria can still grow in the fridge and even at temperatures colder than 2°C.

You can lower your risk of exposure to listeria by:

• choosing safer foods; avoid higher-risk foods (see list above)
• cooking food thoroughly to kill any Listeria bacteria
• eating only foods that were recently prepared
• washing and drying raw fruit and vegetables thoroughly before eating
• refrigerating leftovers quickly; store them in the fridge and eat within two days; reheat leftovers until piping hot (over 75° C); avoid leftovers that won’t be reheated
• washing and drying your hands thoroughly and following good hygiene practices.

More information

For more information on food preparation, storage, and safety, visit Food safety at home | NZ Government or freephone 0800 008 333

To discuss your health and treatment options, speak to your usual GP, hauora or healthcare provider. You can also call Healthline free on 0800 611 116

For more information on listeriosis and how to prevent it, visit the Health New Zealand | Te Whatu Ora website: Listeriosis or contact your local public health service.

To find the contact details for your local public health service, visit National Public Health Service