A patient with Crohn’s disease says she is “lucky to be alive” after she was infected by listeria from a sandwich in a Kent hospital.

Tanya Marston had just been discharged from William Harvey Hospital in Ashford after four weeks receiving treatment for a stomach complaint when she got a call from the hospital.

After around 16 hours at home, a consultant told her blood test results showed she had caught the bug and needed to return to hospital immediately.

The 38-year-old said she is already “hyper-vigilant” with food because stomach bugs can “trigger problems” for her.

Tanya Marston had already been in hospital for four weeks.

She said: “I am quite angry, it's still going over in my head what could have happened.

"I'm lucky. I feel very lucky that my temperature spiked as it did and the nurse in charge acted so quickly.

“I’m very grateful to the hospital for acting so quickly but still there's this thought in my head of ‘how?’

"How could they be handing out sandwiches that could potentially kill me?”

She was back in hospital within two hours of the phone call and seen by the medical director on the ward within five minutes of arriving.

He told her he felt this was linked to cases reported in Manchester and Aintree, where three patients died after eating pre-packaged sandwiches contaminated with listeria.

Ms Marston said she was on intravenous therapy with seven different anti-biotics, one of which was to protect her brain from meningitis.

She has received a letter of apology from the hospital and Public Health England says that it has taken action to contain the outbreak and that the risk to the public is low.

However, ITV correspondent Geraint Vincent said the geographical spread of the outbreak may be much wider than originally thought.

Listeria can be fatal for people who have got pre-existing conditions or who are already sick, which is why hospital patients are particularly vulnerable.

A screengrab from the The Good Food Chain website, based in Staffordshire, which produced the sandwiches Credit: The Good Food Chain

The bacteria in listeria can cause listeriosis.

It is usually caught from eating food containing listeria bacteria.

Listeria infection in healthy people is usually either unnoticed or may cause very mild illness.

However, it can have more serious consequences for some people, particularly those with pre-existing health conditions and pregnant women.

Mild symptoms of listeriosis include a high temperature of 38C or above, aches and pains, chills, feeling sick or vomiting, diarrhoea.

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 bloodstream or brain.

Good food hygiene is paramount to prevent listeriosis.