Ongoing Listeria outbreak linked to smoked fish

The UKHSA, Food Standards Agency and Food Standards Scotland are investigating an outbreak of Listeria monocytogenes linked to smoked fish. This contamination could be particularly unsafe to people who are vulnerable to Listeria infection – including people who are pregnant and people with certain underlying conditions or who are taking medications which can weaken the immune system.

Listeria is a bacterium that causes an illness called listeriosis. It is widespread in the environment and can contaminate a range of food at low or standard refrigeration temperatures. It can be destroyed by thorough cooking. It is of most concern in chilled, ready to eat foods that do not require further cooking, such as smoked fish.

Most people won’t have any symptoms of the infection or will only experience mild symptoms such as vomiting and diarrhoea, which usually pass within a few days without the need for treatment. People who are pregnant are at increased risk of developing listeriosis which can lead to miscarriage, stillbirth, or severe illness in their newborn babies. More serious infection such as severe sepsis and meningitis can develop in those with weakened immune systems or those over 65 years of age.

Whole genome sequencing analysis has identified an outbreak of 12 linked cases of listeriosis since 2020, with 6 of these since January 2022. Cases have been identified in England and Scotland. The majority of these individuals reported eating smoked fish. One case was a pregnant woman.

Given the ongoing outbreak, as a precaution, information for people who are pregnant has been updated to advise that they thoroughly cook smoked fish before eating it. Advice for avoiding listeriosis infection is being updated to include smoked fish as a high-risk product which should be thoroughly cooked before being eaten by anyone in a high risk group.

Stuart McAdam, FSS Head of Incidents, said:

“Due to an outbreak of Listeria monocytogenes linked to smoked fish, we are reminding people who are vulnerable to Listeria infection – including people who are pregnant and people with weakened immune systems – of the risks in consuming smoked fish and asking them to make sure that the smoked fish is always thoroughly cooked including when served as part of a dish before they eat it.

“We are working closely with UK partners across government to ensure that this advice is as clear as possible – members of the public do not need to avoid these products, but should ensure risks are reduced as far as possible.

“You can do this by keeping chilled ready-to-eat smoked fish cold (5⁰C or below), always using products by their use-by date, following the storage and usage instructions on the label, and cooking or reheating smoked fish until it is piping hot right through.”

Professor Saheer Gharbia, Interim Deputy Director Gastrointestinal Infections and Food Safety (One Health) at UKHSA,  said: :

 “Listeria infection in most people is usually either unnoticed or may cause very mild gastrointestinal illness. However, it can have more serious consequences for some people, particularly those with pre-existing health conditions that cause weakened immunity, and people who are pregnant.

“There are certain foods that are more risky, and in light of this outbreak, we are advising pregnant and vulnerable people to thoroughly cook smoked fish before eating it. If you have any concerns about your health please speak to your midwife, GP or hospital specialist team.”

Risk of listeriosis is particularly high but not completely limited to individuals with cancer, organ transplants, patients taking oral steroids, patients undergoing immunosuppressive or cytotoxic treatment including biologics and chemotherapy, people who are pregnant and their new-born babies, those above 65 years of age, those with uncontrolled HIV infection, uncontrolled diabetes, chronic liver or kidney disease, people with an alcohol dependency and those with iron overload.