Listeria Factsheet

What is Listeria?

Listeria is a rare, but potentially life-threatening disease. Although some adults experience only mild infections of the eye and skin, and gastroenteritis, it can lead to severe blood poisoning (septicaemia) or meningitis.

Pregnant women, the elderly and people with weakened immune systems, including those suffering from cancer, AIDS or alcoholism, are more susceptible to listeria. It is particularly dangerous in pregnancy as it can cause a mild 'flu-like' illness which is not serious to the mother but can cause miscarriage, premature delivery, stillbirth or severe illness in a newborn child.

How do you get listeria?

You usually become infected after eating food contaminated with the listeria bacteria. Foods associated with transmission are most often ready-to-eat refrigerated and processed foods such as: pre-prepared cooked and chilled meals, soft cheeses, cold cuts of meat, pâtés and smoked fish.

It is impossible to tell from its appearance whether food is contaminated with listeria. It will look, smell and taste normal.

Listeria is also widespread in the environment and can be found in raw food, soil, vegetation, sewage and in the faeces of many mammals, birds, and fish.

Up to 5 per cent of the population may be carriers of the disease and do not become ill.

Pregnant mothers sometimes transmit the infection to their baby. This can happen in the womb or when giving birth.

H ow long does it take for symptoms to develop and how long will it last?

It can take from one to over 90 days for illness to develop. The average incubation time is about 30 days. A patient with septicaemia or meningitis will be hospitalised for several weeks.

What is the treatment for listeria?

Listeria should be treated promptly with antibiotics. Patients with severe symptoms will need to be treated in hospital.

How can you avoid getting listeria?

Listeria is unusual because it not only grows at normal room temperature and up to about 40° C, but can grow at low temperatures, including refrigeration temperatures of below 5° C. It is, however, killed by cooking food thoroughly in conventional or microwave ovens and by pasteurisation.

• Keep foods for as short a time as possible and follow storage instructions including 'use by' and 'eat by' dates
• Cook food thoroughly, especially meat, ensuring that it is cooked through to the middle
• Keep cooked food away from raw food
• Wash salads, fruit and raw vegetables thoroughly before eating
• Wash hands, knives, and cutting boards after handling uncooked food
• Make sure that the refrigerator is working correctly
• When heating food in a microwave follow heating and standing times recommended by the manufacturer
• Throw away left-over reheated food. Cooked food which is not eaten immediately should be cooled as rapidly as possible and then stored in the refrigerator
• Pregnant women, the elderly, and people with weakened immune systems should not help with lambing or touch the afterbirth

The Health Protection Agency and Listeria

The HPA is involved with detecting cases of infection with listeria, as well as monitoring outbreaks and looking for any patterns or trends which show possible connections between people who are affected. We provide advice on controlling outbreaks and, where possible, track the source, for example, the food that has caused the illness, so that we can stop other people from becoming infected. The HPA is also involved with testing foods for the presence of Listeria monocytogenes and providing advice to all those involved with the food chain to reduce the presence of this bacterium.

More information about listeria is available on our website www.hpa.org.uk/infections/topics_az/listeria/menu.htm.

If you have concerns about your health contact NHS Direct on 0845 4647 or visit the website www.nhsdirect.nhs.uk, or see your family doctor.

This factsheet can also be listeriosis (PDF, 121 KB)

Last reviewed: 27 April 2009