How do I recognise listeriosis?

In healthy people, a listeria infection often occurs without symptoms or with mild flu symptoms, nausea and diarrhoea. Listeriosis may be more severe in young babies, the elderly and people with weakened immune systems. In these people, meningitis or encephalitis, or blood poisoning (sepsis) can occur in rare cases. In a small number of these people, the infection can be fatal.

Pregnant women are more likely to become ill after being infected with listeria. The unborn child can also become infected. This can lead to a miscarriage or premature birth and severe illness of the baby. If a pregnant woman becomes ill from a listeria infection, she can often develop symptoms such as:

• headache
• back pain
• joint pain
• muscle pain
• high fever

Sometimes a pregnant woman will first get stomach flu-like symptoms, such as diarrhoea. This happens especially when they develop listeriosis in the third trimester. During this period, there is also a higher risk of premature birth or death of the unborn child. A pregnant woman who is infected but has no symptoms may, in rare cases, transmit the bacterium to the unborn child.

How do I get listeriosis?

People almost always get infected with listeria by eating contaminated food. Often these are raw ingredients. Also, during food production, 'cross-contamination (in Dutch)' can occur: the bacterium transfers from one product to another, for example via an infected cutting board. Examples of food most commonly contaminated with listeria are:

• soft (mould) cheese made from raw milk
• smoked fish
• cold cuts
• steak tartare
• pâté
• ready-made products, such as raw vegetable salads and ready-made pancakes

The bacterium also occurs in the soil, in animals, in water and on crops. However, listeria is mainly found on food that is stored in the refrigerator for a long time and not heated before it is eaten. The time between getting infected and developing symptoms ranges from several hours to a few months. It usually takes 2 to 4 weeks.

Direct human-to-human contamination almost never happens (with the exception of the infection of an unborn child by the woman carrying the child).

How do I prevent listeriosis?

There are a number of measures for reducing or preventing the risk of listeria infection:

• Set the refrigerator to 4 degrees Celsius. The listeria bacterium grows less quickly in cold conditions.
• Put food that may contain listeria on the bottom shelf in the refrigerator. Do this as soon as possible after purchase or use.
• Always wash raw vegetables well before use.
• Heat food by cooking, baking or roasting it before you eat it. Heat kills the listeria bacterium.
• Do not eat food that can spoil after its expiry date.
• Do not keep food that can spoil for too long. The Netherlands Nutrition Centre's Storage of food fact sheet shows how long a product can be kept after it has been opened.
• Pregnant women are advised not to eat certain products. More information about nutrition during pregnancy can be found on the website of the Netherlands Nutrition Centre.

Can listeriosis be treated?

A doctor can treat listeriosis with medicines.

How common is listeriosis in the Netherlands?

In the Netherlands, 4 out of every million people get infected with the listeria bacterium each year. The disease is most common in people over the age of 65 years. Every year, RIVM receives approximately 85 reports of patients with listeria infection. On average, 5 of them are pregnant.

Is listeriosis dangerous during pregnancy?

Listeriosis is also a rare disease for pregnant women. Pregnant women are more likely to develop symptoms from a listeria infection. The unborn child can also become infected. This happens especially if the person contracts listeriosis in the third trimester. The unborn child could develop sepsis. This can lead to a miscarriage, premature birth or death of the baby. A pregnant woman who is infected but has no symptoms may, in rare cases, transmit the bacterium to the unborn child.

Newborn babies are more likely to develop severe symptoms. They may develop sepsis, meningitis or encephalitis, and die from it.

If you are in the third trimester of your pregnancy, have eaten a potentially contaminated product and have symptoms of a listeria infection (high fever, headache or back, muscle and joint pain), you must inform your GP. They can take this into account in the diagnosis and possible treatment.

Can a person with listeriosis go to childcare, school or work?

Direct human-to-human contamination hardly ever occurs. If a child is feeling well, they can go to their childcare centre or school. However, you should inform the childcare employee or teacher that your child has listeriosis. In consultation with the Municipal Health Service (GGD), they can inform other parents, as their children may be exposed to the same source. Parents can then monitor for the symptoms of listeriosis in their child. Sometimes additional measures are needed at the childcare centre or school.

An adult with listeriosis who feels well can go to work. This does not apply to all professions. Do you work in one of the following sectors?

• healthcare
• childcare (especially for very young children)
• food preparation, such as in a restaurant or butcher's shop

In those cases, you must first consult the GGD/company physician or your employer before returning to work.