The UK Health Security Agency (UKHSA) has declared a national outbreak of salmonella food poisoning after one person died and hundreds more fell ill. While the exact source hasn’t been confirmed, imported eggs or products containing them are the leading suspects. Evidence also points to people catching the bug while eating out, rather than at home, with restaurants and cafes likely playing a role. But there’s still much to uncover. Here’s what we know so far and the questions that remain.
What is salmonella and how do you catch it?
Salmonella are a family of bacteria that typically live harmlessly in the digestive tracts of animals, including cattle, pigs, and chickens. That’s why eggs and poultry are among the foods most commonly associated with the infection. The bacteria are shed in animal faeces, and you can catch the bug by:
- Eating contaminated food that hasn’t been cooked properly
- Drinking contaminated water
- Coming into contact with infected animals
- Cross-contamination, such as mixing raw and cooked food in the kitchen
What are the symptoms?
Symptoms to watch for include stomach cramps, diarrhoea, vomiting, or fever. These usually develop between 12 and 72 hours after infection. Most people recover without needing medical help, but older adults, babies, and those with weakened immune systems are at greater risk of severe illness. Hospital care with fluids and sometimes antibiotics may be needed in such cases. If you’re concerned, contact your GP or out-of-hours service in the first instance.
Can cooking eggs get rid of salmonella?
Yes, cooking eggs and other food thoroughly can prevent infection. Other ways to protect yourself include washing your hands before preparing food, after using the bathroom, and after contact with animals.
Where is the outbreak happening?
The majority of recent cases—199 of the 207—have been in England, including 47 in London and 38 in Yorkshire and Humber. There have been six cases in Scotland, one in Wales, and one in Northern Ireland. While the cases are spread out, scientists used whole-genome sequencing, a comprehensive genetic fingerprinting technique, which revealed that the bacteria involved are all closely related. Tests show only a handful of differences in their DNA sequences, indicating the infections are part of the same outbreak with a common source.
Why are imported eggs considered the most likely source?
Genetic testing of the bacteria suggests similarities with a previous outbreak involving imported eggs. UKHSA experts interviewed 114 people involved in the current outbreak, and their answers indicate that eggs provide the “strongest signal” or clue. Some 24 cases had links to five businesses (which haven’t been named), with 11 people reporting they ate dishes containing eggs. Investigations suggest these premises may use eggs from multiple sources, including imported ones. “At this time there is no identified link to UK-produced eggs or poultry,” the UKHSA says.
Which eggs should you buy?
Jacquelyn McCormick, head of incidents at the Food Standards Agency, says the standard advice remains unchanged: thoroughly cooked eggs that are handled hygienically should not present a food safety risk. Infants, young children, pregnant women, and older adults should only eat runny or raw eggs if they have a British Lion mark or are produced under the Laid in Britain egg assurance scheme. People who are immunocompromised should follow their doctor’s advice. Meanwhile, Dr. Kathleen O’Reilly at the London School of Hygiene and Tropical Medicine recommends checking food hygiene ratings when choosing cafes or restaurants.
How are British eggs kept safe?
The vaccination of commercial hens against common salmonella strains, which began in the mid-1990s in the UK, has been a “major public health success” and has “substantially reduced egg-associated salmonella infections,” according to Dr. Charlotte Hammer at the University of Cambridge. Another quality control measure is the British Lion Scheme, launched in 1998. Suppliers of eggs with the British Lion mark must adhere to a strict code that covers vaccinating hens and a passport system to ensure traceability. Paul Wigley, professor in animal microbial ecosystems at the Bristol Veterinary School, says improved surveillance and detection have also helped. “However, we do still import a large number of eggs and egg products, and salmonella could be contained within these because the countries in which they’re produced don’t use that same level of control,” he added. Mark Williams, chairman of the British Egg Industry Council, said food businesses that import eggs should check their supply lines for vaccination information and ensure all food safety checks have been done.
What do we still not know?
Health experts still need to confirm that eggs are the source. They then need to track where the eggs or egg products came from, and the next step would be to take measures to limit further infections. One challenge is that when a business imports a large number of eggs, they can come from mixed sources. The UKHSA has alerted other countries about this outbreak so they can check for any genetically similar infections. While salmonella infections occur every year in the UK, outbreaks potentially linked to a single food source that lead to hundreds of illnesses are relatively unusual, so scientists will want to examine the factors that led to this situation.
