A salmonella outbreak across the UK has killed one person and infected at least 207 people, the UK Health Security Agency reported.
Public health officials investigating the UK cases have expanded their search for the source to include imported chicken alongside eggs, which were initially suspected. Seven European countries are now affected by the ongoing outbreak.
The UK Health Security Agency first reported British cases earlier this month. Data shows that more than a third of patients for whom information was available required hospital treatment, while bacteria escaped the gut and entered the bloodstream in two cases.
Dr Bharat Pankhania, an expert in communicable diseases, warned against treating the condition lightly. "Some groups are more at risk than others and the infection can enter the bloodstream and become very serious. It can even lead to fatalities," Pankhania told the Daily Mail.
Salmonella bacteria naturally inhabit the intestines of farm animals such as chickens and cattle, often causing no symptoms in the animals. Meat can become contaminated during slaughter from faeces or gut contents, while infected hens produce contaminated eggs.
Contamination can also spread to produce through manure or dirty water, as seen in past outbreaks involving cucumbers, lettuce, and tomatoes. Infected food handlers who fail to wash their hands also transmit the bacteria.
Although thorough cooking kills salmonella, it does not remove all risk. "Hard-boiled eggs are safer than scrambled eggs, which are safer than runny eggs, which are safer than uncooked eggs," Pankhania said, noting that consumers cannot simply wash eggshells because bacteria can live inside.
Pankhania noted that British laying hens are vaccinated against salmonella, making domestic eggs significantly safer than imports from countries with less stringent safety standards. He added that the infectious dose can be low, with slightly dirty hands or a few hundred surviving microbes in a runny egg sufficient to trigger illness.
How salmonella infects the body
When swallowed, salmonella enters the stomach, where stomach acid destroys many microbes. Surviving rod-shaped bacteria pass into the small intestine and attach to cells on the intestinal wall.
Using microscopic needle-like structures, the bacteria inject proteins that hijack the internal machinery of intestinal cells. This forces the cell membrane to fold around the bacteria, drawing them inside to multiply.
Within 12 to 24 hours, the immune system detects the infection and sends white blood cells, including macrophages and neutrophils, to fight the bacteria. Infected cells and immune cells release chemical distress signals called cytokines, triggering severe gut inflammation.
This immune response drives major symptoms by disrupting water absorption and forcing fluid into the intestines, causing abdominal cramps, nausea, and diarrhoea. Cytokines acting on the brain cause fever, chills, and muscle aches.
Diarrhoea can become severe, watery, or bloody if the intestinal lining suffers heavy damage. Most healthy individuals recover within four to seven days as inflammation settles and the gut repairs itself.
High risk groups and medical conditions
Severe complications occur when bacteria breach the intestinal wall and enter the blood, causing a condition known as bacteraemia.
Vulnerable groups include children under five, adults over 65, and individuals with weakened immune systems, such as cancer patients undergoing chemotherapy, organ transplant recipients on immunosuppressants, and people living with HIV or AIDS.
Patients taking high-dose steroids such as prednisolone and dexamethasone for conditions like rheumatoid arthritis, Crohn's disease, ulcerative colitis, severe asthma, and COPD also face higher risk because these medications suppress immune function.
Millions of Britons taking proton pump inhibitors like omeprazole and lansoprazole for acid reflux are similarly exposed. Pankhania explained that these drugs lower stomach acid, removing a key early barrier against food poisoning and increasing susceptibility to salmonella infections.
Severe complications and sepsis risks
Bloodstream invasion can lead to sepsis, a life-threatening reaction where the immune system damages the body's own tissues and organs. Sepsis affects 245,000 Britons and causes nearly 50,000 deaths annually, leading to organ failure and fatal drops in blood pressure.
Warning signs of sepsis include confusion, severe breathlessness, extreme shivering, reduced urine output, mottled or bluish skin, and a feeling of impending doom. Sepsis requires immediate hospital care with antibiotics, intravenous fluids, oxygen, or intensive care treatment.
Once in the bloodstream, salmonella can infect distant organs and bones, causing osteomyelitis, a painful bone infection particularly dangerous to people with sickle cell disease.
The bacteria can also infect the heart valves and lining, causing endocarditis, which strikes one to five per cent of salmonella bacteraemia patients and carries a mortality rate of up to 40 per cent.
In older adults with atherosclerosis, salmonella can infect damaged blood vessels, causing vessel walls to swell and potentially rupture, resulting in fatal internal bleeding. Infections can also spread to the kidneys and urinary tract, especially in patients with kidney stones.
In rare cases, salmonella causes meningitis by infecting the tissues surrounding the brain and spinal cord. Infants, young children, and immunocompromised individuals face the highest risk of meningitis, which causes severe headaches, stiff neck, fever, vomiting, confusion, seizures, lasting brain damage, or death.
Prevention and safe food handling
Pankhania stressed that prevention is essential because damage begins as soon as a systemic infection takes hold. "Prevention is gold. Once somebody has a serious systemic Salmonella infection, the damage has already begun," Pankhania said. "What we can do is reduce the chances of infection happening in the first place."
He advised consumers to choose British eggs marked with the Lion mark, which verifies origin from vaccinated flocks. "When I buy eggs, for example, I can choose British eggs carrying the Lion mark, which come from vaccinated flocks. If I'm buying eggs produced somewhere without equivalent controls, I may not have that same reassurance," he added.
Public health guidance further advises cooking all poultry thoroughly, avoiding washing raw chicken to prevent splashing bacteria, and keeping raw meat strictly separate from ready-to-eat foods.
Kitchen tools and hands should be washed thoroughly after handling raw meat, while chilled foods must be stored below 5C to stop bacterial growth.
