Listeriosis – a foodborne infection caused by listeria monocytogenes bacteria, is not common in New Zealand but can be life-threatening for vulnerable people. Listeria infections are especially dangerous for newborns, older people and anyone with a weakened immune system.
Listeriosis has a very high rate of hospitalisation and is associated with fatality in frail elderly and immuno-compromised people, and foetal loss in pregnancy. In 2024 all 36 reported cases of listeriosis were hospitalised and most of them spent more than seven days in the hospital. There was one death also from listeria.
Listeriosis is caused by eating or drinking food that has high levels of Listeria, a bacterium that is widespread in the environment. Listeria is invisible, has no odour and, unlike most bacteria, can continue to grow when food is refrigerated.
Listeria is particularly dangerous during pregnancy because it can cause miscarriage, premature labour, stillbirth, or infection in the newborn baby. Know which foods to avoid while pregnant.
Similarly, those who are over the age of 65 are at risk as their immune system gets weaker, making it harder for them to fight off harmful foodborne bacteria like Listeria. This means that foods they safely ate in the past may no longer be safe for them to eat.
“Some people may not be aware of this. So, we’re highlighting higher-risk foods while sharing some food-safety advice on how to make them safe to eat,” says New Zealand Food Safety deputy director-general Vincent Arbuckle.
Higher-risk foods include:
- ready-to-eat meat products
- smoked seafood – especially cold smoked fish
- soft cheeses
- uncooked paneer
- unpasteurised dairy products
- uncooked frozen vegetables
- pre-prepared sandwiches & salads
- leafy greens & bagged salad, etc
To lower the risk of getting listeriosis, you can: choose safer foods; heat food to piping hot (over 75°C) before eating; when eating raw fruit and vegetables, wash and dry thoroughly first; only eat food that was recently prepared; refrigerate leftovers quickly and avoid eating leftovers that won’t be reheated and wash and dry your hands thoroughly and follow good food hygiene practices.
“New Zealand Food Safety requires food businesses to manage Listeria in the processing environment and to have strict measures in place to eliminate its presence in products,” says Arbuckle.
Symptoms of Listeria infection can vary. Infection in healthy adults is unlikely to be severe – at most, it will cause mild diarrhoea and flu-like symptoms a few days after eating contaminated food.
Symptoms in pregnant women are also usually mild. They generally take 2 to 3 weeks to appear and can include fever and flu-like symptoms.
In older, perhaps frail, and immuno-compromised people, symptoms usually take 2 to 3 weeks to appear and typically include fever, muscle pain, fatigue and headache.
Cross-contamination of infected food is also a concern as Listeria can spread to different foods and surfaces. For example, if you have brie cheese on a platter with bread and olives, Listeria from the cheese could spread to everything on the platter.
To help prevent cross-contamination, separate high-risk foods from those that are low-risk or already cooked. Use different chopping boards and knives, and wash your hands.
For more information on food safety at home, click here.
