Shigella are a group of germs (bacteria) that can cause gastroenteritis with dysentery. Gastroenteritis is an infection of the bowels (intestines). Diarrhoea is one of the symptoms of gastroenteritis. If the diarrhoea contains blood and mucus, this is known as dysentery. If someone is infected with shigella, the bacteria can pass out in their stools (faeces). Infection with shigella may be caught by drinking water contaminated with infected faeces, eating food prepared using contaminated water or by close contact with someone who has the infection. Infection may occur in people who have travelled to countries with poor sanitation but infection can also be caught in the UK. Treatment is mainly with fluids to prevent or treat lack of fluid in the body (dehydration). In cases where there is blood in the diarrhoea (dysentery) antibiotic medicines are usually needed.
What is gastroenteritis and what is dysentery?
Gastroenteritis is an infection of the bowels (intestines). It can range from a mild tummy (abdominal) upset for a day or two with some mild diarrhoea, to severe diarrhoea and being sick (vomiting) for several days or longer. Many germs (viruses, bacteria and other microbes) can cause gastroenteritis.
Diarrhoea is defined as 'loose or watery stools (faeces), usually at least three times in 24 hours'. Diarrhoea is one of the symptoms of gastroenteritis. If the diarrhoea contains blood and mucus, this is known as dysentery.
Most cases of gastroenteritis do not lead to bloody diarrhoea and so are not dysentery. However, there are a number of microbes that can cause dysentery. These include campylobacter, Entamoeba histolytica, Escherichia coli (E. coli), salmonella and shigella.
See separate leaflets Gastroenteritis in Adults and Gastroenteritis in Children for more information about gastroenteritis. See separate leaflets called Campylobacter, Amoebiasis, E. coli and VTEC O157 and Salmonella for more details about other causes of gastroenteritis. The rest of this leaflet is just about infection caused by shigella.
What is shigella and how do you get it?
Shigella are a group of germs (bacteria) that can cause gastroenteritis with dysentery. Gastroenteritis is an infection of the bowels (intestines). Dysentery caused by shigella is also known as bacillary dysentery. There are four different species of shigella: Shigella dysenteriae, Shigella flexneri, Shigella boydii and Shigella sonnei.
If someone is infected with shigella, the bacteria can pass out in their stools (faeces). Infection may be passed on to others if drinking water is contaminated with infected faeces or if food is washed in contaminated water. Because shigella infection can be passed on by drinking contaminated water or eating contaminated food, shigella can be a cause of food poisoning.
If you have shigella, 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 shigella and who gets it?
Anyone can get shigella infection. However, infection is more common in young children. Commonly, people with shigella infection have travelled to a country where sanitation and hygiene is poor. However, infection can also be caught in the UK. Shigella sonnei is the most common species found in the UK. It tends to cause a mild illness. One group of people recently found to be at risk of shigella are men who have sex with men when contact with the back passage (anus) is involved.
What are the symptoms of shigella?
Some people with shigella infection actually have no symptoms. However, the germs (bacteria) will still be present in their stools (faeces) and they can still pass on the infection to other people.
But most people with shigella infection develop symptoms. Symptoms tend to come on within one to seven days of contact with the bacteria (eg, drinking contaminated water, eating contaminated food). This time period before symptoms appear is known as the 'incubation period'. The usual symptoms are:
- Diarrhoea (which will often contain blood and mucus - dysentery).
- Painful tummy (abdominal) cramps.
- High temperature (fever).
The symptoms tend to last for around five to seven days.
Symptoms can be severe in some people, particularly the young and the elderly. The diarrhoea can be so bad that it can lead to lack of fluid in the body (dehydration). 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.
Symptoms of dehydration in children
Symptoms of dehydration in children include:
- Passing little urine.
- A dry mouth.
- A dry tongue and lips.
- Fewer tears when crying.
- Sunken eyes.
- Being irritable.
- Having a lack of energy (being lethargic).
Symptoms of severe dehydration in children include:
- Pale or mottled skin.
- Cold hands or feet.
- Very few wet nappies.
- Fast (but often shallow) breathing.
Severe dehydration is a medical emergency and immediate medical attention is needed.
Dehydration is more likely to occur in:
- Babies under the age of 1 year (and particularly those under 6 months old). This is because babies don't need to lose much fluid to lose a significant proportion of their total body fluid.
- Babies under the age of 1 year who were a low birth weight and who have not caught up with their weight.
- A breast-fed baby who has stopped breast-feeding during their illness.
- Any baby or child who does not drink much when they have gastroenteritis.
- Any baby or child with severe diarrhoea and vomiting. (For example if they have passed five or more diarrhoeal stools and/or vomited two or more times in the previous 24 hours.)
Symptoms of dehydration in adults
Symptoms of dehydration in adults include:
- Dizziness or light-headedness.
- Muscle cramps.
- Sunken eyes.
- Passing less urine.
- A dry mouth and tongue.
- Becoming irritable.
Symptoms of severe dehydration in adults include:
- Profound loss of energy or enthusiasm (apathy).
- A fast heart rate.
- Producing very little urine.
- Coma may occur.
Severe dehydration is a medical emergency and immediate medical attention is needed.
Dehydration in adults is more likely to occur in:
- Elderly or frail people.
- Pregnant women.
- People with severe diarrhoea and vomiting. In particular, if you are not able to replace the fluid lost with enough drinks.
How is shigella diagnosed?
Shigella infection is usually diagnosed after a sample of your stools (faeces) is sent to the laboratory for testing. If you have a gastroenteritis infection with blood and mucus in your diarrhoea, you should see a doctor who can arrange for a sample of your stools to be tested.
What is the treatment of shigella in children?
Symptoms often settle within a few days or so as a child's immune system is usually able to clear the infection. Children can usually be treated at home. Occasionally, admission to hospital is needed if symptoms are severe or if complications develop.
Fluids to prevent lack of fluid in the body (dehydration)
You should encourage your child to take plenty of fluids. The aim is to prevent dehydration. The fluid lost in their sick (vomit) and/or diarrhoea needs to be replaced. Your child should continue with their normal diet and usual drinks. In addition, they should also be encouraged to drink extra fluids. However, avoid fizzy drinks or large amounts of concentrated fruit juices as these can make diarrhoea worse.
Babies under 6 months old are at increased risk of dehydration. You should seek medical advice if they develop gastroenteritis. Breast-feeds or bottle-feeds should be encouraged as normal. You may find that your baby's demand for feeds increases. You may also be advised to give extra fluids (either water or rehydration drinks) in between feeds.
Rehydration drinks may be advised for children at increased risk of dehydration (see above for whom this may be). They are made from sachets available from pharmacies and on prescription. You should be given instructions about how much to give. Rehydration drinks provide a perfect balance of water, salts and sugar. The small amount of sugar and salt helps the water to be taken up (absorbed) better from the gut (intestines) into the body. If rehydration drinks are not available for whatever reason, make sure you keep giving your child water, diluted fruit juice or some other suitable liquid. If you are breast-feeding, you should continue with this during this time. It is important that your child is rehydrated before they have any solid food.
If your child vomits, wait 5-10 minutes and then start giving drinks again but more slowly (for example, a spoonful every 2-3 minutes). Use of a syringe can help in younger children who may not be able to take sips.
Note: if you suspect that your child is dehydrated or is becoming dehydrated, you should seek medical advice urgently.
Fluids to treat dehydration
If your child is mildly dehydrated, this may be treated by giving them rehydration drinks. Read the instructions carefully for advice about how to make up the drinks and advice about how much to give. The amount can depend on the age and the weight of your child. If you are breast-feeding, you should continue with this during this time. It is important that your child is rehydrated before they have any solid food.
Sometimes a child may need to be admitted to hospital for treatment if they are dehydrated. Treatment in hospital usually involves giving rehydration solution through a special tube called a nasogastric tube. This tube passes through your child's nose, down their throat and directly into their stomach. An alternative treatment is with fluids given directly into a vein (intravenous fluids).
Eat as normally as possible once any dehydration has been treated
Correcting any dehydration is the first priority. However, if your child is not dehydrated (most cases), or once any dehydration has been corrected, encourage your child to have their normal diet. Do not 'starve' a child with gastroenteritis. This used to be advised but is now known to be wrong. So:
- Breast-fed babies should continue to be breast-fed if they will take it. This will usually be in addition to extra rehydration drinks (described above).
- Bottle-fed babies should be fed with their normal full-strength feeds if they will take them. Again, this will usually be in addition to extra rehydration drinks (described above).
- Older children - offer them some food every now and then. However, if he or she does not want to eat, that is fine. Drinks are the most important and food can wait until their appetite returns.
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. Also in shigella, they may make the condition worse. However, you can give paracetamol or ibuprofen to ease a high temperature (fever) or headache.
If symptoms are severe or persist for several days or more, or there is blood in the stools (faeces), a doctor may ask for a sample of the diarrhoea. If shigella is confirmed, in some cases an antibiotic medication may be needed. Your child is likely to need an antibiotic if there is blood in their diarrhoea. An antibiotic may also be prescribed if your child has a condition where their immune system is not working as well as normal - for example due to chemotherapy or an illness such as AIDS
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.
What is the treatment of shigella in 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).
The following are commonly advised until symptoms ease:
Fluids - have lots to drink
The aim is to prevent lack of body fluid (dehydration), or to treat dehydration if it has developed. (Note: if you suspect that you are dehydrated, you should contact a doctor.)
- As a rough guide, drink at least 200 mls after each watery stool (bout of diarrhoea).
- This extra fluid is in addition to what you would normally drink. For example, an adult will normally drink about two litres a day but more in hot countries. The above '200 mls after each watery stool' is in addition to this usual amount that you would drink.
- If you are sick (vomit), wait 5-10 minutes and then start drinking again but more slowly. For example, a sip every 2-3 minutes but making sure that your total intake is as described above.
- You will need to drink even more if you are dehydrated. A doctor will advise on how much to drink if you are dehydrated.
For most adults, fluids drunk to keep hydrated should mainly be water. Also, ideally, include some fruit juice and soups. It is best not to have drinks that contain a lot of sugar, such as cola or pop, as they can sometimes make diarrhoea worse.
Rehydration drinks are recommended for people who are frail, or over the age of 60, or who have underlying health problems. They are made from sachets that you can buy from pharmacies. (The sachets are also available on prescription.) You add the contents of the sachet to water. Rehydration drinks provide a good balance of water, salts and sugar. The small amount of sugar and salt helps the water to be absorbed better from the gut (intestines) into the body. They do not stop or reduce diarrhoea. Do not use home-made salt/sugar drinks, as the quantity of salt and sugar has to be exact.
Eat as normally as possible
It used to be advised to 'starve' for a while if you had gastroenteritis. However, now it is advised to eat small, light meals if you can. Be guided by your appetite. You may not feel like food and most adults can do without food for a few days. Eat as soon as you are able - but don't stop drinking. If you do feel like eating, avoid fatty, spicy or heavy food at first. Plain foods such as wholemeal bread and rice are good foods to try eating first.
Medicines to reduce the diarrhoea (such as loperamide) should not be used if you have shigella. This is because they can make the symptoms worse.
As explained above, in some cases, your doctor may ask for a sample of the diarrhoea. This is sent to the laboratory to look for infecting germs (microbes such as bacteria, parasites, etc). A course of antibiotic medicine is sometimes needed. You may need antibiotics if your symptoms are severe, or if you have blood in your diarrhoea. You may also need antibiotics if you have a condition where the immune system is not working as well as normal - for example, due to chemotherapy or an illness such as AIDS. Where an antibiotic is needed, usually one called ciprofloxacin is used.
Note: if you are receiving treatment for shigella infection and your condition is not improving within 48 hours, or if your condition worsens, you should contact your doctor or arrange for urgent medical review as needed. You should also urgently see a doctor:
- If you develop severe vomiting.
- If you are worried that you may be dehydrated, or are becoming dehydrated.
- If you have a persistent high temperature.
- If you develop abdominal swelling (distension).
- If you develop blood in your stools.
The same applies for your child.
Preventing the spread of shigella to others
If you (or your child) have shigella, 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 shigella is confirmed, you should inform your employer and stay away from work until your doctor advises you when it is safe to return.
If you have shigella infection and you work with vulnerable groups of people such as the elderly, the unwell or the young, you should inform your employer. Your doctor also has the duty of reporting shigella infection to your local public health authority.
Are there any complications that can develop?
Complications are uncommon in the UK. Those who are older are more likely to develop complications. Complications 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 your 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 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 (arthritis), inflammation of the tubes that carry urine (urethritis) and eye inflammation (either conjunctivitis or uveitis).
- Haemolytic uraemic syndrome. This is a serious condition where there is anaemia, a low platelet count in the blood, and kidney damage. It may be caused by poisons (toxins) produced by some types of shigella germs (bacteria). It is more common in children. If recognised and treated, most people recover well.
- Spread of infection to other parts of your body, causing more widespread infection (sepsis)
- Irritable bowel syndrome is sometimes triggered by shigella infection.
- Lactose intolerance can sometimes occur for a period of time after infection of your bowels (gastroenteritis) caused by shigella. This is known as 'secondary' or 'acquired' lactose intolerance. Your gut (intestinal) lining can be damaged by the episode of gastroenteritis. This leads to lack of an enzyme called lactase that is needed to help your body digest a sugar in milk, called lactose. Lactose intolerance leads to bloating, tummy (abdominal) pain, wind and watery stools after drinking milk. The condition gets better over time after the infection is over and the intestinal lining heals. It is more common in children.
- Fits (seizures) may occur in children, especially if they have a high temperature (fever.)
- Toxic megacolon. This is a condition where the lower part of the bowel swells up. This causes severe tummy pain and bloating.
- Reduced effectiveness of some medicines. During any episode of gastroenteritis, certain medicines that you may be taking for other conditions or reasons may not be as effective. This is because the diarrhoea and/or being sick (vomiting) means that reduced amounts of the medicines are taken up (absorbed) into your body. Examples of such medicines are those for epilepsy, diabetes and contraception. Speak to your doctor or practice nurse if you are unsure of what to do if you are taking other medicines and have gastroenteritis.
Reporting the food poisoning episode
Any suspected case of food poisoning from eating takeaway or restaurant food should be reported to the local Environmental Health Office. This is so that the business can be investigated by environmental health officers. Further actions may be taken if there is a problem with their food hygiene practices. It is hoped that this will 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 or confirms that your child has food poisoning, they are also required by law to report this.
Can shigella be prevented?
In general, good hygiene is essential to prevent the spread of many infections to others and to reduce your chance of picking up infections from others. Hand washing is the most important thing that you and your child can do. In particular, always wash your hands and dry them thoroughly, and teach children to wash and dry theirs:
- After going to the toilet (and after changing nappies or helping an older child to go to the toilet).
- Before preparing or touching food or drinks.
- Before eating.
In addition to this, when travelling to areas with poor sanitation, you should avoid eating or drinking the following to help reduce your chance of getting shigella infection. This is because shigella is often passed on by drinking contaminated water or eating food prepared using contaminated water. Avoid:
- Tap water.
- Ice cream.
- Ice cubes.
- Fruit that has already been peeled. (If eating fruit, peel it yourself, so that you know it has not been in contact with contaminated water.)
Sealed bottled water, tea, coffee and alcohol are thought to be safe to drink.
Men who have sex with men should wash their hands after touching a partner's back passage (anus) or coming into contact with a condom used during anal sex. Condoms should be changed between anal sex and oral sex. Mouth to anus contact (also known as 'rimming') is very high-risk and should be avoided.
Studies are underway throughout the world, looking at developing a vaccine that may be able to prevent shigella infection.
Further reading and references
Shigella: guidance, data and analysis; Public Health England
Diarrhoea and vomiting in children under 5; NICE Clinical Guideline (April 2009)
Gastroenteritis; NICE CKS, July 2015 (UK access only)
Barry EM, Pasetti MF, Sztein MB, et al; Progress and pitfalls in Shigella vaccine research. Nat Rev Gastroenterol Hepatol. 2013 Apr10(4):245-55. doi: 10.1038/nrgastro.2013.12. Epub 2013 Feb 19.
Shigella; Microbiology in Pictures
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