More than 50 sickened and 10 hospitalised in mystery UK salmonella outbreak – as experts say source ‘unknown’

A MYSTERY salmonella outbreak that occurred in the UK last year has been under investigation by the UK Health Security Agency (UKHSA).

More than 50 people were reported to have fallen ill and 10 people hospitalised.

Testing revealed all cases of infection were caused by the rare Salmonella Blockley strain, more commonly seen in East Asia and the US.

An incident management team including Public Health Scotland, Public Health Wales, and the Public Health Agency in Northern Ireland, with the Food Standards Agency (FSA) and Food Standards Scotland (FSS) held their first meeting on the incidences in September 2024.

The meeting notes, which are only now being reported, admitted the source of the outbreak is currently “unknown”.

Between July 27 and August 24 last year, 54 cases were reported.

This included 36 people in England, seven in Wales, and 11 in Scotland.

The patients ranged in age from two to 85, with the most affected age group 50 to 59 year olds, with 13 cases reported.

And 10 of 21 people with information available were hospitalised.

Like all types of salmonella, Salmonella Blockley causes acute gastrointestinal illness characterised by diarrhoea, stomach cramps, and fever.

There's no evidence to suggest it's worse than other types of salmonella, but it has shown high rates of multi drug resistance.

Some studies have suggested patients may experience symptoms for up to 10 years after an infection.

A case report published in a medical journal in 2006, suggested Salmonella Blockley triggered arthritis in a previously healthy young man, which persisted for a decade.

Salmonella Blockley is primarily associated withchicken and eggs, but can also be found in other foods like smoked eel and vegetables.

The UKHSA said a national level investigation was opened because of the number of patients infected – also because the apparent population at risk was those older than 50, and because of suspicion of an internationally distributed vehicle of infection.

No indication of travel before illness was found.

Genetically similar strains of Salmonella Blockley have been identified in one European country, it added, with possible cases in another.

This indicates the involvement of an international supply chain, although the source of the outbreak remains unknown.

It's believed there have been no further cases of Salmonella Blockley, but a UKHSA spokesperson has confirmed the investigation is ongoing.

Experts from the European Centre for Disease Prevention and Control said there was an increase in Salmonella Blockley cases in 2023 with 83 cases reported – the most reported in the past 10 years.

However, it's not known if this rise is linked to the outbreak in the UK.