Three hospital patients have died in England following a listeria outbreak linked to pre-packed sandwiches, health officials revealed today.

The outbreak has been linked to six seriously ill patients, three of whom died at Aintree University Hospital and Manchester University NHS Foundation Trusts.

Sandwiches and salads linked to the cases have been withdrawn and the supplier, The Good Food Chain, which supplies 43 NHS trusts in the UK, has voluntarily ceased production while the probe continues.

The first case showed symptoms on April 25 while the most recent case was reported on May 15, a Public Health England spokeswoman said.

Sandwiches and salads were withdrawn on May 25, as soon as a link with the cases was suspected.

It is understood that some of the products were sold at hospitals while others were given to patients.

Three hospital patients have died after a listeria outbreak linked to pre-packed sandwiches and the supplier, The Good Food Chain (pictured), has voluntarily ceased production

Aintree University Hospital NHS Foundation Trust was one of the two hospital trusts affected

Meat was produced by North Country Cooked Meats, based in Salford, Greater Manchester

This firm had been supplied with meat produced by North Country Cooked Meats which subsequently produced a positive test result for the outbreak strain of listeria.

This business and North Country Quality Foods, which they distribute through, have also voluntarily ceased production. There are no cases in Scotland or Wales.

A spokesman for North Country Cooked Meats said: 'At this stage the company is currently cooperating fully with the environmental health and the FSA in their investigations and a further statement will be issued in due course.'

WHAT IS LISTERIOSIS? Most people that catch listeriosis, caused by bacteria called listeria, will only experience mild symptoms, such as vomiting and diarrhoea. Other symptoms of the infection can include a high temperature of 38C or above, aches and pains, and chills, according to the NHS. Listeria monocytogenes (stock) as found in the pre-packaged food sold at hospitals However, more serious complications can develop in those with weakened immune systems, babies, the elderly and pregnant women. Many foods can harbour listeria, but it is usually found in unpasteurised milk, soft cheeses and ready-to-eat foods, such as prepacked sandwiches. Listeria is widespread in the environment and can be found in raw food and soil, and in the droppings of many mammals, birds, and fish. Around 180 cases of listeriosis are confirmed every year in England, according to figures. It strikes around 850 annually in the US. HOW CAN YOU AVOID LISTERIOSIS? wash your hands regularly with soap and water

wash fruit and vegetables before eating them

store ready-to-eat foods as recommended by the manufacturer

make sure all hot food is steaming hot all the way through Advertisement

Listeria infection in healthy people is usually either unnoticed or may cause very mild illness, but it can have more serious consequences for some people, particularly those with pre-existing health conditions and pregnant women.

Health officials insisted that the risk to the public remains low and people should only seek medical attention if they develop symptoms.

The sandwiches and salads affected are no longer being produced while investigations continue - and the affected products were withdrawn from hospitals when the links to the listeria infections were first identified.

Dr Nick Phin, deputy director at the national infection service at Public Health England, said: 'Our thoughts are with the families of those patients who have died.

'We, along with the FSA, colleagues in local authorities and the NHS have worked quickly to determine the likely cause of this outbreak and taken action to reduce the risk to the public's health.

'To date, there have been no associated cases identified outside healthcare organisations, and any risk to the public is low.'

The Manchester trust covers five hospitals - Manchester Royal Infirmary, Manchester Royal Eye Hospital, Royal Manchester Children's Hospital, St Mary's Hospital and Wythenshawe Hospital.

Dr Colin Sullivan, chief operating officer at the Food Standards Agency, said: 'Our sympathies are with the families of those patients who have tragically passed away.

'We have taken action along with local authorities to minimise the risk based on the evidence so far. The FSA will continue to investigate how the outbreak occurred and if further steps are required to protect vulnerable groups.'

Listeriosis is a rare infection and for most people it goes unnoticed or there are mild symptoms of gastroenteritis that usually last a short time without the need for treatment.

The time between exposure to the organism and the development of the illness can be up to 70 days.

Occasionally, however, a more serious infection develops and spreads to the blood stream or brain. This can happen in people who have serious underlying health conditions and can also occur in pregnant women.

The Good Food Chain, which supplied the sandwiches, is based in Stone, Staffordshire