Listeriosis is a rare infection caused by bacteria called listeria. It usually goes away on its own, but it can make some people seriously ill.

Listeriosis is usually caused by eating food contaminated with listeria bacteria.

Listeria can contaminate a wide range of foods, but most infections are caused by eating chilled, ready-to-eat foods, such as:

• cold, cooked sliced meats and cured meats
• smoked and cured fish – including in sushi
• cooked shellfish
• soft mould-ripened cheeses (such as camembert and brie) and blue-veined cheeses
• pâté
• pre-prepared sandwiches and salads
• pre-cut fruit (such as pre-packed melon slices)
• unpasteurised milk
• dairy products made from unpasteurised milk

These foods do not always contain listeria. If you have eaten them recently, you do not need to do anything unless you get symptoms of the infection.

Although it's less common, you can also catch listeriosis from:

• someone else who has it – for example, if you eat food they've handled when they've not washed their hands
• close contact with farm animals – especially sheep and cows that are giving birth

In most people, listeriosis has no symptoms or only causes mild symptoms for a few days, such as:

• a high temperature
• aches and pains
• chills
• feeling or being sick
• diarrhoea

If you're pregnant, you may also have a stomach ache or notice your baby moving less than usual.

Babies with listeriosis may also be irritable and feed less than usual.

Listeriosis is not usually serious for most people.

But some people have a higher risk of serious problems, including:

• anyone who is pregnant
• newborn babies
• people with a condition that weakens their immune system, such as cancer, diabetes, liver disease or kidney disease
• people having treatment that weakens their immune system, such as chemotherapy or steroid tablets

Older people are also at higher risk of getting seriously ill from listeriosis, and this risk increases with age.

If you get listeriosis while you're pregnant, there is a risk it could cause miscarriage or stillbirth.

In babies and people with a weakened immune system, listeriosis can sometimes lead to serious and life-threatening problems such as sepsis or meningitis.

Ask for an urgent GP appointment or get help from NHS 111 if:

Call 999 or go to A&E if you or your child:

For most people, listeriosis is mild and gets better in a few days.

You can usually look after yourself at home by resting and drinking plenty of fluids.

If you're at a higher risk of getting seriously ill (for example, you're pregnant or have a weakened immune system), you may need antibiotics.

Find out how to treat diarrhoea and vomiting

There are some simple things you can do to reduce your risk of getting listeriosis.

If you're pregnant or have a weakened immune system, you should avoid eating ready-to-eat cold-smoked or cured fish products, such as smoked salmon or gravlax (unless cooked until steaming hot).

If you're pregnant, you should also avoid eating other foods that have the highest risk of causing listeriosis.

These include:

• some soft cheeses (including brie and camembert) – unless cooked until steaming hot
• all types of pâté – including vegetable pâté
• unpasteurised milk or dairy products
• any undercooked food

If you're pregnant, you should also avoid close contact with farm animals that are giving birth or have recently given birth.

Find out which foods to avoid during pregnancy