Salmonella cases in England are the highest they've been in a decade , according to recent UK Health Security Agency (UKHSA) data. There was a 17% increase in cases observed from 2023 to 2024 - culminating in 10,388 detected infections last year. Children and older adults accounted for around a fifth of cases.
Author
- Rob Kingsley
Professor, Microbiology, Quadram Institute
Although the number of infections caused by foodborne diseases such as Salmonella had broadly decreased over the last 25 years, this recent spike suggests a broader issue is at play. A concurrent increase in Campylobacter cases points to a possible common cause that would affect risk of both foodborne pathogens - such as changes in consumer behaviour or food supply chains.
While the UK maintains a high standard of food safety, any increase in the incidence of pathogens such as Salmonella warrants serious attention.
Salmonella is a species of bacteria that is one of the most common causes of foodborne illnesses globally. The bacteria causes salmonellosis - an infection that typically causes vomiting and diarrhoea.
Most cases of salmonellosis don't require medical intervention. But approximately one in 50 cases results in more serious blood infections. Fortunately, fatalities from Salmonella infections in the UK are extremely rare - occurring in approximately 0.2% of all reported infections.
Salmonella infections are typically contracted from contaminated foods. But a key challenge in controlling Salmonella in the food supply chain lies in the diverse range of foods it can contaminate.
Salmonella is zoonotic, meaning it's present in animals , including livestock. This allows it to enter the food chain and subsequently cause human disease. This occurs despite substantial efforts within the livestock industry to prevent it from happening - including through regular testing and high welfare practices.
Salmonella can be present on many retail food products - including raw meat, eggs, unpasteurised milk, vegetables and dried foods (such as nuts and spices). When present, it's typically at very low contamination levels. This means it doesn't pose a threat to you if the product is stored and cooked properly.
Vegetables and leafy greens can also become contaminated with Salmonella through cross-contamination, which may occur from contaminated irrigation water on farms, during processing or during storage at home. As vegetables are often consumed raw, preventing cross-contamination is particularly critical.
Spike in cases
It's premature to draw definitive conclusions regarding the causes of this recent increase in Salmonella cases. But the recent UKHSA report suggests the increase is probably due to many factors .
One contributing factor is that diagnostic testing has increased. This means we're better at detecting cases. This can be viewed as a positive, as robust surveillance is integral to maintaining a safe food supply.
The UKHSA also suggests that changes in the food supply chain and the way people are cooking and storing their food due to the cost of living crisis could also be influential factors.
To better understand why Salmonella cases have spiked, it will be important for researchers to conduct more detailed examinations of the specific Salmonella strains responsible for the infections. While Salmonella is commonly perceived as a singular bacterial pathogen, there are actually numerous strains (serotypes).
DNA sequencing can tell us which of the hundreds of Salmonella serotypes are responsible for human infections. Two serotypes, Salmonella enteritidis and Salmonella Typhimurium, account for most infections in England.
Although the UKHSA reported an increase in both serotypes in 2024, the data suggests that Salmonella enteritidis has played a more significant role in the observed increase. This particular serotype is predominantly associated with egg contamination.
Salmonella enteritidis is now relatively rare in UK poultry flocks thanks to vaccination and surveillance programmes that were introduced in the 1980s and 1990s. So the important question here is where these additional S enteritidis infections are originating.
Although the numbers may seem alarming, what the UKHSA has reported is actually a relatively moderate increase in Salmonella cases. There's no reason for UK consumers to be alarmed. Still, this data underscores the importance of thoroughly investigating the underlying causes to prevent this short-term increase from evolving into a longer-term trend.
Staying safe
The most effective way of lowering your risk of Salmonella involves adherence to the "4 Cs" of food hygiene :
1. Cleaning
Thoroughly wash hands before and after handling any foods - especially raw meat. It's also essential to keep workspaces, knives and utensils clean before, during and after preparing your meal.
2. Cooking
The bacteria that causes Salmonella infections can be inactivated when cooked at the right temperature. In general, foods should be cooked to an internal temperature above 65°C - which should be maintained for at least ten minutes . When re-heating food, it should reach 70°C or above for two minutes to kill any bacteria that have grown since it was first cooked.
3. Chilling
Raw foods - especially meat and dairy - should always be stored below 5°C as this inhibits Salmonella growth . Leftovers should be cooled quickly and also stored at 5°C or lower.
4. Cross-contamination
To prevent Salmonella passing from raw foods to those that are already prepared or can be eaten raw (such as vegetables and fruit), it's important to wash hands and clean surfaces after handling raw meat, and to use different chopping boards for ready-to-eat foods and raw meat.
Most Salmonella infections are mild and will go away in a few days on their own. But taking the right steps when storing and preparing your meals can significantly lower your risk of contracting it.
Rob Kingsley receives funding from the Biotechnology and Biological Sciences Research Council (BBSRC), Bill and Melinda Gates Foundation
