It’s not ‘just’ food poisoning: Experts reveal terrifying risks of salmonella and how to stay safe …amid major UK outbreak linked to imported eggs and chicken
The ongoing salmonella outbreak battering the UK has already killed one and left at least 207 severely unwell – throwing into sharp relief just how serious the infection can be.
With seven European countries now affected, public health officials are rushing to identify the source – and yesterday the investigation widened to include chicken, rather than just eggs, which were initially suspected.
Now experts, speaking to the Daily Mail, have revealed in painful detail the extensive risks posed by salmonella – from agonising stomach cramps and relentless diarrhoea to severe dehydration, blood poisoning, organ failure and even death.
The first British cases in the current outbreak were reported by the UK Health Security Agency (UKHSA) earlier this month.
More than a third of patients for whom information was available required hospital treatment, while in two cases the bacteria escaped the gut and entered the bloodstream – a potentially life-threatening complication.
Dr Bharat Pankhania, an expert in communicable diseases says it’s vital not to dismiss salmonella as ‘just food poisoning’.
He adds: ‘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.’
So how can bacteria lurking in something as innocuous as an egg or piece of chicken unleash such devastation – and what exactly happens after salmonella gets inside your body, and who is most at risk of getting severely unwell?
Public health officials are rushing to identify the source of the salmonella outbreak – and the investigation has widened to include chicken, not just eggs, which were initially suspected
How salmonella evolved to beat the body’s defences
Salmonella are bacteria that can live in the intestines of farm animals, including chickens and cattle, sometimes without causing them obvious harm.
During slaughter, bacteria from faeces or gut contents can contaminate meat, while infected hens can produce contaminated eggs.
Salmonella can also spread to fruit and vegetables through manure or contaminated water – previous outbreaks have been linked to cucumbers, lettuce and tomatoes – or via infected people who fail to wash their hands before preparing food.
Problems begin when contaminated food is eaten. Thorough cooking kills salmonella, but as Dr Pankhania explains, this is not foolproof.
‘Hard-boiled eggs are safer than scrambled eggs, which are safer than runny eggs, which are safer than uncooked eggs,’ he says. ‘You can take appropriate measures, but nothing in life is 100 per cent safe.
‘Salmonella can be inside an egg, so you can’t simply wash the shell.
‘British laying hens are vaccinated against salmonella, which means British eggs are far safer – but the risk is higher with eggs imported from countries where food-safety controls may be less stringent.’
After contaminated food is swallowed, the bacteria reach the stomach, where powerful gastric acid kills many of them.
But salmonella has evolved to survive these hostile conditions, allowing some bacteria to pass into the small intestine.
Dr Pankhania says: ‘The infectious dose – the number of bacteria needed to cause an infection – can be low.
‘Slightly dirty hands or a few hundred microbes in an egg that haven’t been killed because you’re eating it runny can be enough to cause serious problems.’
In the gut, the microscopic, rod-shaped bacteria attach themselves to cells lining the intestinal wall. Using tiny, needle-like structures, they inject proteins that hijack the cells’ internal machinery.
This forces the cell membrane to fold around the bacterium, drawing it inside.
Once safely within the cell, Salmonella begins to multiply.
Within 12 to 24 hours, the immune system detects the invasion and begins to mount a defence. White blood cells including macrophages and neutrophils are mobilised to fight the bacteria.
Public health officials are scrambling to identify the source – and yesterday the investigation widened to include chicken, rather than just eggs, which were initially suspected
Infected cells and immune cells release chemical distress signals known as cytokines, triggering intense inflammation in the gut and summoning yet more immune cells to the site of the infection.
It is this furious immune response – as much as the bacteria themselves – that is responsible for many of the symptoms of salmonella poisoning.
The inflammation disrupts normal water absorption and forces fluid into the intestines, triggering abdominal cramps, nausea and diarrhoea.
Cytokines released by the immune system also act on the brain, raising body temperature and causing fever, chills and muscle aches.
Over the following days, diarrhoea can become severe and watery – even bloody if the intestinal lining is badly damaged – while nausea and vomiting may also occur.
For most healthy people, the infection clears within four to seven days as inflammation subsides and the gut repairs itself.
But in some cases, the bacteria breach the gut wall and enter the bloodstream – which is when serious problems can begin.
Who is most at risk of severe complications
When salmonella breaches the gut wall and enters the circulation it causes bacteraemia – bacteria in the blood – which can lead to life-threatening complications.
Most at risk are people with weakened immune systems, including cancer patients undergoing chemotherapy, organ transplant recipients taking immunosuppressants and people with HIV/AIDS.
Children under five and adults over 65 are also more vulnerable.
Another group are those taking high-dose steroids such as prednisolone and dexamethasone, used to treat conditions including rheumatoid arthritis, Crohn’s and ulcerative colitis, and severe asthma and COPD. At sufficiently high doses, these drugs suppress the body’s ability to fight infection.
Millions of Britons taking proton pump inhibitors (PPIs) for acid reflux may also be more susceptible to salmonella.
The drugs, including omeprazole and lansoprazole, reduce production of stomach acid.
Dr Pankhania says: ‘These medicines also weaken one of the body’s first lines of defence against food poisoning – the highly acidic environment that kills many Salmonella bacteria before they can reach the intestines.
‘That’s why long-term use of PPIs has been associated with increased susceptibility to intestinal infections including salmonella.’
One of the greatest dangers once salmonella reaches the bloodstream is sepsis – when the body’s response to infection begins damaging its own tissues and organs.
It affects 245,000 Britons and kills almost 50,000 each year, and can cause dangerously low blood pressure, multi-organ failure and death.
Warning signs include confusion, extreme shivering, severe breathlessness, passing little or no urine and mottled or bluish skin. An overwhelming sense of ‘impending doom’ can also be a red flag.
Sepsis requires urgent hospital treatment with antibiotics and, where needed, intravenous fluids and oxygen. Severe cases may require intensive care.
Heart problems, bone pain and deadly internal bleeding
Once salmonella enters the bloodstream, it can travel to almost any part of the body and establish infections far from the gut.
One possible complication is osteomyelitis, a painful bone infection. While rare, people with the blood disorder sickle cell disease are at particularly high risk.
The bacteria can also invade the heart, causing endocarditis – an infection of its inner lining and valves – which studies suggest affects roughly one to five per cent of patients with salmonella bacteraemia.
Up to 40 per cent of those who develop it die.
Salmonella can also infect damaged blood vessels, particularly in older adults with atherosclerosis – the narrowing and hardening of arteries associated with heart disease.
This can weaken the vessel wall, causing it to swell and potentially rupture, resulting in catastrophic internal bleeding.
The kidneys and urinary tract can also become infected, particularly in people with existing problems such as kidney stones.
More rarely, salmonella can infect the tissues surrounding the brain and spinal cord, causing meningitis. Babies, young children and people with weakened immune systems are particularly vulnerable.
It can cause severe headache, stiff neck, fever, vomiting, confusion and seizures, and can lead to lasting neurological damage or death. Suspected meningitis requires immediate emergency treatment.
Dr Pankhania says: ‘Prevention is gold. Once somebody has a serious systemic Salmonella infection, the damage has already begun.
‘What we can do is reduce the chances of infection happening in the first place.
‘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.’
Experts also advise cooking poultry thoroughly, never washing raw chicken – which can splash bacteria around the kitchen – and keeping raw meat separate from ready-to-eat foods.
Hands and kitchen equipment should be washed carefully after handling raw meat, while chilled foods should be kept below 5C to prevent bacteria multiplying.
