London School of Hygiene & Tropical Medicine

On 18 August 2026 the UK Health Security Agency (UKHSA) declared a national outbreak of Salmonella Enteritidis in the UK.

207 cases have been confirmed between 11 August 2025 and 1 August 2026, with the majority reported in 2026. Of those affected, 38% were admitted to hospital and one person has died.

The UKSHA has initiated an investigation into the outbreak to identify the source of the illness. Initial findings suggest it may be linked to eggs imported from outside the UK.

Dr Kathleen O'Reilly, Associate Professor at London School of Hygiene & Tropical Medicine, said: “Salmonella is a bacterial infection that can cause diarrhoeal disease, and especially in the vulnerable can lead to more severe symptoms. I read with great sadness that in this outbreak a person has died.

“The investigation teams at UKHSA noticed an increased number of cases with the same type of Salmonella – this often indicates an outbreak. The response initially includes looking for more cases and ensuring that cases of diarrhoeal disease have samples so microbiologists can carry out analysis. Teams will investigate using cases to identify possible common sources of infection.

“From this work, it appears that eating eggs outside of the home, possibly from eggs produced internationally could be a common source. However, at this stage this information is not ‘definitive’ and as the outbreak progresses it is possible other sources may be identified. Investigations will continue to establish likely sources and remove from the food chain. Salmonella infection is common in many animals, including livestock such as chickens and pigs. Considerable efforts are in place to limit infection in animals and reduce the risk to humans.

“Previous research has estimated that less than 10% of Salmonella cases require hospitalisation, so it seems initially concerning that 38% in this outbreak have been admitted to hospital. As the epidemic progresses, this number might change, especially as Salmonella cases are often underreported.

“Making sure that eggs are fully cooked before being eaten is best, as always. Hygiene while preparing food is important, especially washing hands with soap and chopping boards after preparation. All catering outlets have a food hygiene rating, so looking at these while deciding where to eat would be wise. If an omelette is still runny, cook it for longer to kill off any bacteria if they are present. If you do get ill with diarrhoea or stomach cramps, take it easy, drink plenty of fluids, and cases will often resolve after a few days. If the illness is in young children, elderly, or other vulnerable groups, it would be sensible to contact your GP or ring 111 to talk with a health specialist.”

Dr Damien Tully, Associate Professor at the Medical Research Council/Uganda Virus Research Institute and London School of Hygiene & Tropical Medicine (MRC/UVRI and LSHTM) Uganda Research Unit said: “This is a sizeable outbreak, but the number of confirmed cases is likely to be just the tip of the iceberg. Many Salmonella infections cause relatively short-lived gastrointestinal illness and people may recover without ever being tested, meaning the true number of infections associated with an outbreak can be considerably higher than the number identified through laboratory surveillance.

“One of the striking features of this outbreak is that genomic sequencing has allowed more than 200 cases across the UK to be connected. These are people who may have no obvious connection to one another, but the bacteria causing their infections are genetically very closely related. This provides investigators with an important clue that they may be looking at a common source and helps focus the search for where the infections are coming from.

“The genetic relationship with a previous outbreak associated with imported eggs is particularly interesting and gives investigators an important lead. However, establishing the source will require the genomic evidence to be combined with information from cases about what and where they ate, alongside tracing products back through the food supply chain.

“Reassuringly, the outbreak has been identified and is being actively investigated by a number of public health agencies. For most healthy people, Salmonella causes an unpleasant but self-limiting illness, although it can occasionally cause serious disease, particularly in young children, older adults and people with weakened immune systems. Good food hygiene remains important: wash your hands before preparing or eating food, avoid cross-contamination in the kitchen, and make sure foods such as eggs, poultry and meat are cooked thoroughly.”

Brendan Wren, Professor of Microbial Pathogenesis at LSHTM, said "Salmonella enteritidis causes severe diarrhoea and can be fatal in the elderly or immunocompromised individuals. It is readily transmitted through the handling or consumption of food. Using DNA fingerprinting the outbreak of at 200 cases appears to be from a single source. The most likely source is from the consumption of eggs or egg related products such as mayonnaise. The outbreak control team at the UKHSA are actively investigating the source and routes of transmission of the outbreak."

This is a rapid reaction to a breaking news story.