Listeria is a rare but potentially life threatening disease. Most healthy adults are likely to suffer little more than mild flu-like symptoms or gastroenteritis; however pregnant women, the elderly and people with weakened immune systems are more susceptible.

Infection with Listeria usually occurs by eating contaminated foodstuffs, with pre-prepared cooked and chilled meals, soft cheeses, cold cuts of meat, and smoked fish being most commonly associated. Listeria is one of the more unusual food poisoning bacteria because it can grow at temperatures ranging from normal room temperature down to as low as 5°C (refrigeration temperature).

Poor refrigeration and failure to follow shelf life labelling can result in the multiplication of the bacteria to unsafe levels. It is impossible to tell from the appearance, smell or taste that food is contaminated with Listeria which makes the control of it so important. Killing of the bacteria is possible by thorough cooking in a conventional oven or microwave.

On average it takes thirty days for illness to develop after ingesting food contaminated with Listeria. In the worst cases symptoms can progress to severe blood poisoning or meningitis and may have the patient hospitalised for a number of weeks.

The following is a list of simple steps to minimise the risk:

• Make sure your fridge is set to 5°C or below and is functioning correctly
• Food taken out of chilled storage should be eaten within four hours - after this time the food should be thrown away
• Keep cooked and raw foods separate
• Follow the storage instructions printed on the label
• Cook food thoroughly ensuring that it is cooked in the centre
• Don't use food after its 'use by' date
• Use opened foods within two days, unless the manufacturer's instructions state otherwise
• Throw away left over re-heated food
• Cooked food that is not eaten should be cooled as quickly as possible and then stored within the refrigerator