Britain’s ongoing salmonella outbreak has already left one death and at least 207 people seriously unwell – highlighting just how serious the infection can be.
With seven European countries affected, public health officials are rushing to identify the source – and yesterday the investigation expanded to include chicken, rather than just eggs as initially suspected.
Now, speaking to the Daily Mail, experts have revealed in painful detail the extensive risks of salmonella – from painful stomach cramps and brutal diarrhea to severe dehydration, blood poisoning, organ failure and even death.
The first UK cases of 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 from the intestines and entered the bloodstream – a potentially life-threatening complication.
Dr. Bharat Pankhania, an expert on communicable diseases, says it is crucial 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 wreak such havoc — and what exactly happens after salmonella gets into your body, and who is most at risk of becoming seriously ill?
Public health officials are rushing to identify the source of the salmonella outbreak — and the investigation has expanded to include chicken, not just eggs, which was initially suspected
How salmonella evolved to defeat the body’s defenses
Salmonella are bacteria that can live in the intestines of farm animals, including chickens and cattle, sometimes without causing apparent harm.
During slaughter, bacteria from feces or intestinal contents can contaminate the meat, while infected chickens can produce contaminated eggs.
Salmonella can also spread to fruits and vegetables through manure or contaminated water – previous outbreaks have been linked to cucumbers, lettuce and tomatoes – or through infected people who do not wash their hands before preparing food.
The problems start when contaminated food is eaten. Thorough cooking kills salmonella, but as Dr. Pankhania explains, it’s 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 percent safe.
‘Salmonella can be in an egg, so you can’t just wash the shell.
‘British laying hens are vaccinated against salmonella, meaning British eggs are much safer – but the risk is greater if eggs are imported from countries where food safety controls may be less stringent.’
After contaminated food is swallowed, the bacteria reach the stomach, where powerful stomach acid kills many of them.
But salmonella has evolved to survive these hostile conditions, allowing some bacteria to enter the small intestine.
Dr. Pankhania says: ‘The infectious dose – the number of bacteria needed to cause an infection – may be low.
‘A little dirty hands or a few hundred microbes in an egg that haven’t been killed because you eat it in liquid form can be enough to cause serious problems.’
In the intestine, the microscopic, rod-shaped bacteria attach to cells along the intestinal wall. Using small, needle-like structures, they inject proteins that hijack the cell’s internal machinery.
This forces the cell membrane to fold around the bacterium, drawing it inward.
Once safely in the cell, Salmonella begins to multiply.
Within 12 to 24 hours, the immune system detects the invasion and begins to defend itself. White blood cells, including macrophages and neutrophils, are mobilized to fight the bacteria.
Public health officials are working to identify the source – and yesterday the investigation was expanded to include chicken, rather than just eggs, which was initially suspected
Infected cells and immune cells release chemical distress signals known as cytokines, causing intense inflammation in the intestines and summoning even more immune cells to the site of the infection.
It is this intense immune response – like 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, causing abdominal cramps, nausea and diarrhea.
Cytokines released by the immune system also act on the brain, raising body temperature and causing fever, chills and muscle aches.
In the following days, the diarrhea may become severe and watery – even bloody if the intestinal wall is severely damaged – while nausea and vomiting may also occur.
In most healthy people, the infection clears up within four to seven days as the inflammation subsides and the intestines repair themselves.
But in some cases, the bacteria break through the intestinal wall and enter the bloodstream – and that’s when serious problems can begin.
Who is most at risk for serious complications
When salmonella penetrates the intestinal wall and enters the bloodstream, it causes bacteremia – bacteria in the blood – which can lead to life-threatening complications.
People with weakened immune systems are most at risk, 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 doses of steroids such as prednisolone and dexamethasone, which are used to treat conditions such as rheumatoid arthritis, Crohn’s disease and ulcerative colitis, and severe asthma and COPD. At high enough doses, these medications suppress the body’s ability to fight infections.
Millions of Britons taking proton pump inhibitors (PPIs) for acid reflux may also be more susceptible to salmonella.
The medications, including omeprazole and lansoprazole, reduce the production of stomach acid.
Dr. Pankhania says: ‘These drugs also weaken one of the body’s first lines of defense against food poisoning: the highly acidic environment that kills many Salmonella bacteria before they can reach the intestines.
‘Therefore, long-term use of PPIs is associated with increased susceptibility to intestinal infections, including salmonella.’
One of the biggest dangers once salmonella reaches the bloodstream is sepsis – when the body’s response to infection begins to damage its own tissues and organs.
It affects 245,000 Britons and kills almost 50,000 people a year, and can cause dangerously low blood pressure, multi-organ failure and death.
Warning signs include confusion, extreme chills, severe shortness of breath, little or no urination, and mottled or bluish skin. An overwhelming sense of ‘impending doom’ can also be a warning sign.
Sepsis requires urgent hospital treatment with antibiotics and, where necessary, intravenous fluids and oxygen. Severe cases may require intensive care.
Heart problems, bone pain and fatal internal bleeding
Once salmonella enters the bloodstream, it can spread to almost any part of the body, causing infections far from the intestines.
A possible complication is osteomyelitis, a painful bone infection. Although rare, people with the blood disorder sickle cell disease are at particularly high risk.
The bacteria can also enter the heart and cause endocarditis – an infection of the lining and valves – which research shows affects about one to five percent of patients with salmonella bacteremia.
Up to 40 percent of those who develop it die.
Salmonella can also infect damaged blood vessels, especially 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 possibly rupture, leading to catastrophic internal bleeding.
The kidneys and urinary tract can also become infected, especially in people with existing problems such as kidney stones.
In rarer cases, salmonella can infect the tissues surrounding the brain and spinal cord, causing meningitis. Infants, young children and people with weakened immune systems are particularly vulnerable.
It can cause severe headaches, stiff neck, fever, vomiting, confusion and seizures, and can lead to permanent neurological damage or death. Suspected meningitis requires immediate emergency treatment.
Dr. Pankhania says: ‘Prevention is gold. Once someone has a severe systemic Salmonella infection, the damage has already begun.
‘What we can do is reduce the risk of infection in the first place.
‘For example, when I buy eggs, I can choose British eggs with the Lion brand, from vaccinated flocks. If I buy eggs produced somewhere without equivalent controls, I may not have the same peace of mind.”
Experts also recommend 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 refrigerated food should be kept below 5 degrees Celsius to prevent bacteria from multiplying.
