An outbreak of listeria, which is being linked to ready-to-eat smoked fish, has prompted a warning from health officials.

People over the age of 65, who are pregnant or have weakened immune systems are being told to thoroughly cook any ready to eat smoked products to avoid the risk of food poisoning.

Ready to eat smoked fish refers to chilled smoked fish products that would not normally be cooked at home before being eaten.

However an ongoing outbreak of Listeria monocytogenes, a bacteria which is particularly unsafe for vulnerable groups susceptible to a Listeria infection, is causing concern.

Listeriosis is a form of food poisoning caused by the bacterium Listeria monocytogenes. Most people who are affected get mild gastroenteritis, which subsides in a few days, but certain individuals are particularly at risk of very severe illness such as meningitis and life-threatening sepsis while Listeriosis in pregnancy can cause miscarriages and severe sepsis or meningitis in newborns.

An investigation has identified 14 linked cases of listeriosis since 2020 in England and Scotland, eight of these since January 2022, with the majority of those affected having reported eating smoked fish before falling ill. One case, says the Health Security Agency, has been a pregnant woman.

While the risk of becoming seriously ill is low, says the FSA, those who are vulnerable are being told to now take extra precautions such as cooking the ready-to-eat fish again at home until it is piping hot, keeping it in the fridge so it remains cold at 5C or below and never eating the fish past its use-by date.

Professor Saheer Gharbia, Interim Deputy Director Gastrointestinal Infections and Food Safety at UKHSA explained: "Most people won’t have any symptoms of the infection or will only experience mild symptoms such as abdominal pain or diarrhoea, which usually pass within a few days without the need for treatment.

"However, some people are at higher risk of much more serious illness, including those over 65, people who are pregnant or new-born babies, and those with weakened immune systems including people undergoing immunosuppressive treatment, and people with chronic liver or kidney disease.

"In light of this ongoing outbreak, we are advising pregnant and vulnerable people to only eat ready to eat smoked fish that has been thoroughly cooked to reduce the risk of listeriosis. If you have any concerns about your health please speak to your midwife, GP or hospital specialist team."