Listeria and pregnancy, the elderly and people with weakened immune systems


What is listeria?

Listeriosis is a comparatively rare form of foodborne illness, but it can be a very serious disease in pregnant women, people with poor immune systems and the elderly who will need to avoid certain foods see this additional Listeria advice. It has also caused occasional outbreaks of mild gastroenteritis in healthy people.

The symptoms are usually described as ‘flu-like’, although vomiting and discoloured urine can occur. Miscarriage can result if a pregnant woman is infected, even if she doesn’t show the symptoms. The time from infection to symptoms can be anywhere between 8 to 90 days.

Listeria is widely found in the environment so most raw foods are likely to be contaminated. Listeria is easily killed by heat, although cooked foods can easily become re-contaminated through poor food handling after cooking.

This is one of the few pathogens that can grow in the refrigerator, so ready to eat food should never be stored in the fridge too long. Although it can grow in the fridge, it will do so only very slowly so make sure your refrigerator is keeping your food at or less than 5 °C. Never eat packaged food after its use by date.

Listeria are bacteria that can cause the serious illness, listeriosis, in some people. Eating foods contaminated with Listeria is the most common way of contracting the illness.

Watch this short video about listeria

Who is most at risk?

People at higher risk of listeriosis include pregnant women, their unborn and newborn babies, the elderly and other people whose immune systems have been weakened by illness or drugs (for example: cancer patients, organ transplant recipients, and people on drugs like cortisone).

What are the symptoms of listeriosis?

In healthy adults and children, listeriosis causes few or no symptoms and may be mistaken for a mild viral infection or flu. Symptoms may include headache, fever, tiredness and aches and pains. Less common symptoms include diarrhoea, nausea and abdominal cramps.

For people with weakened immune systems, symptoms can progress to more serious forms of illness including septicaemia (blood infection), meningitis (infection and inflammation of membranes surrounding the brain) and even death.

It can take weeks after infection for symptoms to appear so sufferers may not be aware they have listeriosis and may not seek medical advice. Symptoms in pregnant women may appear mild, but listeriosis can cause miscarriage, premature birth, or stillbirth. It is important that pregnant women who have symptoms of listeriosis seek medical attention immediately.

How to avoid Listeria?

If you (or someone in your household) has a weakened immune system, or is pregnant, the best way to avoid Listeria is to eat freshly cooked or freshly prepared food.

Try to avoid foods which have a higher risk of Listeria contamination such as:

  • cold meats from delicatessen counters and sandwich bars, and packaged, sliced ready-to-eat meats
  • cold cooked ready- to-eat chicken (whole, portions, or diced)
  • pre-prepared or pre-packaged fruit or vegetable salads, including those from buffets and salad bars
  • chilled seafood such as raw oysters, sashimi and sushi, smoked ready-to-eat seafood and cooked ready-to-eat prawns
  • soft, semi-soft and surface-ripened cheeses such as brie, camembert, ricotta, blue and feta
  • refrigerated paté or meat spreads
  • soft serve ice cream
  • unpasteurised dairy products.

You can further reduce your risk of listeriosis by following these food safety tips:

  • avoid foods that are past their ‘best before’ or ‘use by’ date
  • refrigerate leftovers promptly and use within 24 hours, or freeze
  • cook foods thoroughly
  • reheat foods until it is steaming hot
  •  check this advice from Food Standards Australia New Zealand on making safer food choices.

For more information about listeriosis see Healthdirect