Salmonella | Symptoms, Treatment and Causes (2024)

What is salmonella?

Salmonella are germs (bacteria) that are a common cause of food poisoning. Food poisoning occurs when food or water contaminated with germs (microbes), poisons (toxins) or chemicals is eaten or drunk. Typically, food poisoning causes gastroenteritis, an infection of the gut (intestines). Infectious diseases of the gut lead to diarrhoea and sometimes also to being sick (vomiting).

In the salmonella group there are over 2,500 different strains (subtypes).

One type of salmonella, Salmonella typhi (S. typhi), can cause typhoid fever. This is a serious disease which can be life-threatening if not treated quickly with antibiotic medicines. It causes diarrhoea at first and then high temperature (fever), headache, stomach cramps, skin rash, feeling sick (nausea) and loss of appetite.

Another type of salmonella, Salmonella paratyphi (S. paratyphi), can cause paratyphoid fever. This is a similar illness to typhoid fever but symptoms are generally milder. Typhoid and paratyphoid are almost exclusively caught abroad in countries with poor sanitation. It can be passed on in the stools (faeces) and in the urine of infected people. Infection with S. typhi and S. paratyphiis uncommon in the UK. Infection with various other strains is quite common.

The rest of this leaflet is only about food poisoning caused by strains of salmonella other than S. typhi and S. paratyphi. See the separate leaflet calledTyphoid and Paratyphoid Fever for more information about these other infections.

How do you get salmonella?

Salmonella germs (bacteria) may be found in the gut of many animals, including wild animals, farm animals and pets. Poultry (chickens, turkeys, etc) are especially likely to carry salmonella. So, salmonella can contaminate meat (including poultry), raw eggs from chickens which have not been vaccinated, milk and other dairy products that we may eat.

Adequate cooking of meat (including poultry) usually kills salmonella bacteria. Humans can become infected if they eat undercooked meat that is contaminated with salmonella. Eating raw or undercooked eggs, or consuming milk or other dairy products contaminated with salmonella, can also pass on salmonella infection to humans.

Sometimes, other foods such as fruit and vegetables can become contaminated with salmonella through contact with manure used to help them grow. Shellfish may also become contaminated if they are in contact with infected sewage in the water.

Dogs, cats and rodents can sometimes become infected with salmonella. Tortoises and terrapins are also common salmonella carriers. Contact with infected animals or their stools (faeces) can also allow transmission of infection to humans. The bacteria can pass from your hands into your mouth and then your gut (intestines) where they can then multiply and cause symptoms.

Once you have salmonella, you may also spread the infection to your close contacts if you do not follow strict hygiene measures to prevent the spread of infection to others (see below).

How common is salmonella and who gets it?

Salmonella food poisoning is quite common. In England and Wales in 2016, there were 8,630 confirmed cases compared with 8,558 in 2015. As many people with food poisoning are not tested, there are probably many more cases than were confirmed. In the UK, numbers of cases of salmonella have gradually dropped over the past years. It is thought this is due to the policy of vaccinating hens against salmonella. The eggs from vaccinated hens are safe to eat. This is demonstrated by the red Lion stamp you may see on UK eggs.

Salmonella can affect anyone of any age. In most cases it does not cause severe symptoms. However, there are certain groups of people who are more likely to develop severe symptoms. They include:

• Young children.
• The elderly.
• People whose immune systems are not working properly (for example, people undergoing treatment for cancer, people on long-term steroid treatment, people with AIDS, etc).
• People with long-term conditions of their guts such as ulcerative colitis or Crohn's disease.

Because it is possible for salmonella to be spread from person to person, outbreaks can occur, particularly in institutions such as elderly care or nursing homes.

Salmonella symptoms

The typical symptoms are diarrhoea and stomach cramps. The diarrhoea can sometimes be bloody. You may also feel sick (have nausea) and be sick (vomit) and you can develop a high temperature (fever). Symptoms tend to come on within 12-36 hours of eating the contaminated food or being in contact with the infected animal. This time period before symptoms appear is known as the 'incubation period'.

In most people, symptoms are relatively mild and improve within 4-7 days without any specific treatment. However, sometimes, symptoms can be more severe and/or complications can occur. If symptoms are severe, a lack of fluid in the body (dehydration) can occur. You should consult a doctor quickly if you suspect that you or your child are becoming dehydrated. Mild dehydration is common and is usually easily reversed by drinking lots of fluids. Severe dehydration can be fatal unless quickly treated because the organs of your body need a certain amount of fluid to function.

For more information about dehydration symptoms in children and adults see our separate leaflet calledDehydration.

How is salmonella diagnosed?

Many people will recognise food poisoning from their typical symptoms and, if these symptoms are mild, they do not usually need to seek medical advice or receive specific medical treatment. So, you may have salmonella infection that is not 'confirmed'.

However, in some circ*mstances, you may need to seek medical advice when you have food poisoning (see below about when to seek medical advice). The doctor or nurse may ask you questions about recent travel abroad or any ways that you may have eaten or drunk contaminated food or water. They will also usually check you for signs of lack of fluid in the body (dehydration). They may check your temperature, pulse and blood pressure. They may also examine your tummy (abdomen) to look for any tenderness.

The doctor or nurse may ask you to collect a stool (faeces) sample. The sample of your stool is sent to the laboratory for testing. Salmonella is confirmed if the germ (bacteria) is found in your stool sample. Food is sometimes tested for salmonella in outbreaks.

A stool sample is not always needed. Your doctor is likely to suggest one in certain situations, such as:

• If you have recently been abroad.
• If you are very unwell.
• If you have blood or pus in your stools (faeces).
• If your diarrhoea is not settling after a week.
• If you have recently been in hospital or had antibiotic treatment.
• If you have another medical condition, particularly one which affects your immune system.
• If the doctor is not sure you have food poisoning or a gut infection (gastroenteritis).
• If your job involves handling food.

The reason a stool sample is not always needed is that in many cases knowing what germ you have does not make any difference to the treatment you need. Most cases of salmonella get better on their own even before the stool test result is back.

When should I seek medical advice?

Children

If your child has gastroenteritis from any cause (including possible food poisoning caused by salmonella), you should seek medical advice in the following situations:

• If your child is under the age of 6 months.
• If your child has an underlying medical condition (for example, heart or kidney problems, diabetes, history of premature birth).
• If your child has a high temperature (fever).
• If you suspect a lack of fluid in the body (dehydration) is developing (see earlier).
• If your child appears drowsy or confused.
• If your child is being sick (vomiting) and is unable to keep fluids down.
• If there is blood in their diarrhoea or vomit.
• If your child has severe tummy (abdominal) pain.
• Infections caught abroad.
• If your child has severe symptoms, or if you feel that their condition is getting worse.
• If your child's symptoms are not settling (for example, vomiting for more than 1-2 days, or diarrhoea that does not start to settle after 3-4 days).
• If there are any other symptoms that you are concerned about.

Adults

If you have gastroenteritis from any cause (including possible food poisoning caused by salmonella), you should seek medical advice in any of the following situations:

• If you suspect that you are becoming dehydrated.
• If you are vomiting a lot and unable to keep fluids down.
• If you have blood in your diarrhoea or your vomit.
• If you have severe abdominal pain.
• If you have severe symptoms, or if you feel that your condition is becoming worse.
• If you have a persisting high fever.
• If your symptoms are not settling; for example, vomiting for more than 1-2 days, or diarrhoea that does not start to settle after 3-4 days.
• Infections caught abroad.
• If you are elderly or have an underlying health problem such as diabetes, epilepsy, inflammatory bowel disease, kidney disease.
• If you have a weakened immune system because of, for example, chemotherapy treatment, long-term steroid treatment, HIV infection.
• If you are pregnant.
• If you suspect that you may have contracted food poisoning from eating restaurant or takeaway food (see below).
• If your job involves preparing food for other people.
• If there are any other symptoms that you are concerned about

Salmonella treatment

Children

Most children with salmonella do not need any specific treatment. The symptoms usually improve in a few days as their immune system has time to clear the infection. Children with salmonella can usually be cared for at home. Occasionally, admission to hospital is needed if symptoms are severe, or if complications develop.

You should encourage your child to take plenty of fluids. The aim is to prevent lack of fluid in the body (dehydration). The fluid lost in their sick (vomit) and/or diarrhoea needs to be replaced.

However, if your child is not dehydrated (most cases) or once any dehydration has been corrected, encourage your child to have their normal diet.

For information about what to give children with salmonella to eat and drink, see our separate leaflet calledAcute Diarrhoea in Children.

Medication is not usually needed

You should not give medicines to stop diarrhoea to children under 12 years old. They sound attractive remedies but are unsafe to give to children, due to possible serious complications. However, you can giveparacetamol or ibuprofen to ease a high temperature (fever) or headache.

If symptoms are severe or persist for several days or more, a doctor may ask for a sample of the diarrhoea. This is sent to the laboratory to look for infecting germs (bacteria, parasites, etc) including salmonella. If salmonella is found in the sample, antibiotics are not usually required. However a very short course of an antibiotic may be needed if:

• Your child is less than 6 months old.
• Your child has another illness which affects their immune system, or is on medication which affects their immune system.
• Your child has heart valves which are not normal.
• The infection has spread elsewhere in the body (other than the gut).

Probiotics are generally not recommended for children with gastroenteritis or food poisoning from any cause. This may change if further research shows that they are helpful.

Antisecretory medicines are a newer group of treatments. They are designed to be used with rehydration treatment. They reduce the amount of water that is released into the gut during an episode of diarrhoea. They can be used for children who are older than 3 months of age. Racecadotril is the only antisecretory medicine available in the UK at the moment and is only available on prescription. It is not available in Scotland on prescription as it is felt there is not enough evidence yet about how effective it is.

Adults

Symptoms often settle within a few days or so as your immune system usually clears the infection. Occasionally, admission to hospital is needed if symptoms are severe, or if complications develop (see below).

For information about what to eat and drink during a Salmonella infection, see our separate leaflet calledGastroenteritis.

Medication
Antidiarrhoeal medicines are not usually necessary. However, a medicine called loperamide may be advised in some situations. For example, to help you over a special event such as a wedding, or if you have difficulty reaching the toilet quickly. Loperamide works by slowing down your gut's activity and it can reduce the number of trips that you need to make to the toilet. You can buy loperamide from pharmacies. The adult dose of loperamide is two capsules at first. This is followed by one capsule after each time you pass some diarrhoea, up to a maximum of eight capsules in 24 hours. You should not take loperamide for longer than five days.

Note: although loperamide is usually safe, there have been reports of very serious gut problems developing in some people who have taken loperamide. These problems were mainly in people who had severe inflammation of the gut. So, do not use loperamide or any other antidiarrhoeal medicine if you pass blood or mucus with the diarrhoea or if you have a high temperature (fever). Also, people with certain conditions should not take loperamide. Pregnant women should not take loperamide. Therefore, to be safe, read the leaflet that comes with the medicine.

Paracetamol or ibuprofenis useful to ease a high temperature or headache.

Antibiotic medicines may sometimes be needed to treat salmonella in some situations. This may be necessary if:

• The infection has spread elsewhere in the body (other than the gut).
• You are over the age of 50.
• You have a weakened immune system.
• You have heart valve problems.

If needed the antibiotic most often used is ciprofloxacin.

Racecadotril is occasionally used in adults as well as children.

Salmonella prevention

If you (or your child) have salmonella, the following are recommended to prevent the spread of infection to others:

• Wash your hands thoroughly after going to the toilet. Ideally, use liquid soap in warm running water but any soap is better than none. Dry properly after washing. If your child wears nappies, be especially careful to wash your hands after changing nappies and before preparing, serving, or eating food.
• If a potty has to be used, wear gloves when you handle it, dispose of the contents into a toilet, then wash the potty with hot water and detergent and leave it to dry.
• Don't share towels and flannels.
• Don't prepare or serve food for others.
• If clothing or bedding is soiled, first remove any stools (faeces) into the toilet. Then wash in a separate wash at as high a temperature as possible.
• Regularly clean with disinfectant the toilets that you use. With hot water and detergent, wipe the flush handle, toilet seat, bathroom taps, surfaces and door handles at least once a day. Keep a cloth just for cleaning the toilet (or use a disposable one each time).
• Stay off work, school, college, etc, until at least 48 hours after the last episode of diarrhoea or being sick (vomiting). Avoid contact with other people as far as possible during this time.
• Food handlers: if you work with food and develop diarrhoea or vomiting, you must inform your employer and immediately leave the food-handling area. If salmonella is confirmed, you should inform your employer and stay away from work until at least 48 hours after the last episode of diarrhoea or vomiting. Antibiotics are sometimes given to clear the infection.
• If you have salmonella infection and you work with vulnerable groups of people such as the elderly, the unwell or the young, you should inform your employer.

How to prevent salmonella

The Foods Standards Agency is responsible for disease control and prevention in relation to foodborne illness in the UK. It has identified the '4 Cs' to help improve food safety and prevent food poisoning, including food poisoning caused by salmonella.

Cleanliness

• Keep work surfaces and utensils clean.
• Wash and dry your hands regularly but especially after going to the toilet, before preparing food, after handling raw food and before touching 'ready-to-eat' food.
• Don't prepare food for others if you have diarrhoea or are being sick (vomiting).
• Cover any sores or cuts on your hands with a waterproof plaster before you touch food.
• Change dishcloths and tea towels regularly.

You should also wash your hands after touching pets or animals, after visiting farms and after gardening, to help avoid salmonella infection.

Cooking

• Make sure that you cook food thoroughly, especially meat. This will kill germs (bacteria). Food should be cooked right through and be piping hot in the middle.
• If you are reheating food, it needs to be cooked right through and be piping hot in the middle.
• Don't reheat food more than once.

You should also wash raw fruits and vegetables before you eat them. Don't drink water thought to be unsafe (including avoiding drinks containing ice cubes that may have been made from unsafe water). This includes untreated water from rivers, lakes and streams. Drink pasteurised or boiled milk.

Where possible, eat eggs which have been laid by hens vaccinated against salmonella, indicated in the UK by the red Lion stamp. If eating eggs which do not have this stamp, or in countries where this programme does not exist, avoid raw or runny eggs.

Chilling

• Food that needs to be chilled or refrigerated, should be. If food is left out of the fridge, bacteria may multiply to levels that can cause food poisoning.
• Your fridge needs to be kept between 0°C and 5°C. Also, don't leave the door open unnecessarily.
• Cool leftover food quickly and then refrigerate. Taking it out of the cooking pot and putting it into a shallow container can speed the cooling process up.

Cross-contamination

This occurs when bacteria pass from foods (commonly raw foods) to other foods. It can occur if foods touch directly, if one food drips on to another, if your hands, or utensils or equipment, such as knives or cutting boards, touch one food and then another.

• Wash your hands after touching raw foods.
• Separate raw and cooked or 'ready-to-eat' foods.
• Keep raw meat in a sealable container at the bottom of the fridge.
• Don't use the same surface or cutting board for preparing raw and ready-to-eat foods.
• Make sure that knives and utensils are cleaned after preparing raw foods.

In addition to these measures, as reptiles and amphibians, including terrapins and tortoises, can commonly carry salmonella bacteria, they should be kept with caution. You should supervise any contact with children, particularly very young children. You should not keep them where people with weakened immune systems may come into contact with them.

Are there any complications that can develop?

Complications are uncommon in the UK. They are more likely in the very young, or in the elderly. They are also more likely if you have an ongoing (chronic) condition such as diabetes or if your immune system is not working normally. (For example, if you are taking long-term steroid medication or you are having chemotherapy treatment for cancer.)

Possible complications include the following:

• Salt (electrolyte) imbalance and lack of fluid (dehydration) in your body. This is the most common complication. It occurs if the salts and water that are lost in your stools (faeces), or when you are sick (vomit), are not replaced by you drinking adequate fluids. If you can manage to drink plenty of fluids then dehydration is unlikely to occur, or is only likely to be mild, and will soon recover as you drink. Severe dehydration can lead to a drop in your blood pressure. This can cause reduced blood flow to your vital organs. If dehydration is not treated, your kidneys may be damaged. Some people who become severely dehydrated need a 'drip' of fluid directly into a vein. This requires admission to hospital. People who are very young, elderly or pregnant are more at risk of dehydration.
• Reactive complications. Rarely, other parts of your body can 'react' to an infection that occurs in your gut (intestines). This can cause symptoms such as joint inflammation (reactive arthritis), skin inflammation and eye inflammation (either conjunctivitis or uveitis).
• Spread of infection to other parts of your body such as your blood vessels, heart valves, bones or brain. Fortunately this is rare.
• Persistent diarrhoea syndromes may rarely develop - for example:
• Irritable bowel syndrome is sometimes triggered by a bout of food poisoning.
• Lactose intolerance can sometimes occur for a period of time after food poisoning. This is known as 'secondary' or 'acquired' lactose intolerance. This is more common in children. Your child's gut lining can be damaged by the episode of gastroenteritis. This leads to lack of a chemical (enzyme) called lactase that is needed to help the body digest a sugar (lactose) that is in milk. Lactose intolerance leads to bloating, tummy (abdominal) pain, wind and watery stools after drinking milk. The condition gets better over time as the gut lining heals.
• Guillain-Barré syndrome may rarely be triggered by salmonella infection. This is a condition that affects the nerves throughout your body and limbs, causing weakness and sensory problems. See the separate leaflet called Guillain-Barré syndrome for more details.
• Reduced effectiveness of some medicines. During any episode of food poisoning, certain medicines that you may be taking for other conditions or reasons may not be as effective. This is because the diarrhoea and/or vomiting mean that reduced amounts of the medicines are absorbed into your body. Examples of such medicines are those for epilepsy, diabetes and contraception. Speak with your doctor or practice nurse if you are unsure of what to do if you are taking other medicines and have food poisoning.

Reporting the food poisoning episode

If you suspect that you or your child have salmonella or any other type of food poisoning from eating takeaway or restaurant food, you should report this to your local Environmental Health Office. This is so that the business can be investigated by environmental health officers and further actions may be taken if there is a problem with their food hygiene practices. This will hopefully help to reduce the chance that other people will get food poisoning. You can find your local food standards enforcer from the Food Standards Agency Report a Food Problem.

If your doctor suspects that you have food poisoning, or salmonella infection is confirmed from your stool (faeces) sample, they are also required by law to report this.