Viruses, Bacteria, and Parasites in the Digestive Tract

What are viruses, bacteria, and parasite?

Viruses, bacteria, and parasites are living organisms that are found all around us. They exist in water and soil, on the surfaces of foods that we eat and on surfaces that we touch, such as countertops in the bathroom or kitchen. Some bacteria live in and on our bodies and do not cause problems. Other kinds of bacteria (as well as parasites and viruses) can make us quite ill if they invade our bodies. Bacteria and viruses can live outside of the human body (for instance, on a countertop) sometimes for many hours or days. Parasites, however, require a living host in order to survive.

Bacteria and parasites can usually be destroyed with antibiotics. On the other hand, antibiotics cannot kill viruses. Children with viral illnesses can be given medications to make them comfortable, but antibiotics are ineffective against treating these infections.

Bacteria, viruses, and parasites can cause a wide variety of illnesses, and can infect any of the organs of the body. Viruses are often responsible for respiratory illnesses (such as the common cold) and digestive illnesses (such as diarrhea). Bacteria can infect any part of the body, but often cause diarrhea when they invade the digestive tract.

What is diarrhea?

Diarrhea can be caused by a variety of bacteria, viruses, and parasites. Children can also have diarrhea without having an infection, such as when diarrhea is caused by food allergies or as a result of taking medications (such as antibiotics). A child is considered to have diarrhea when the child's bowel movements are both more frequent than usual and looser and more watery than usual.

Children with diarrhea may have additional symptoms including nausea, vomiting, stomach aches, headache, or fever.

How does a child usually come in contact with bacteria, viruses, or parasites that cause diarrhea?

When touching the stool of an infected person (such as when touching soiled diapers)
When touching an object contaminated with the stool of an infected person, and then ingesting the germs--this usually occurs by touching the mouth with a contaminated hand (can occur at day care centers or at home in areas where diapered babies play)
By ingesting contaminated food or water

Why is infection with these organisms a concern?

Viruses, bacteria, and parasites that invade the digestive tract usually cause diarrhea. Large amounts of water are lost with the diarrhea, leading to dehydration in children. Children become dehydrated much quicker than adults, and this can lead to serious problems if fluids are not replaced. Infections caused by parasites and a few types of infections caused by bacteria may also need treatment with medications.

Also, children with a severely weakened immune system are at risk for more serious disease. Symptoms may be more severe and could lead to serious illness. Examples of persons with weakened immune systems include those with HIV/AIDS, cancer and transplant patients who are taking certain immunosuppressive drugs, and those with inherited diseases that affect the immune system.

Common bacteria, viruses, and parasites that cause diarrhea

Bacteria

	E. coli
Description	Escherichia coli O157:H7 is just one of the hundreds of strains of the bacterium Escherichia coli (E. coli). Most strains of E. coli are harmless and live in the intestines of healthy humans and animals. E. coli, however, produces a powerful toxin that can cause a severe infection. (The combination of letters and numbers in the name of the bacterium refers to the specific markers found on its surface and distinguishes it from other types of E. coli.) The CDC recognizes E. coli as a foodborne illness. Infection often leads to bloody diarrhea, stomach cramps, vomiting, and fever.
Transmission	Most E. coli illness has been associated with eating undercooked, contaminated ground beef. E. coli bacteria live in the intestines of healthy cattle and, although the number of organisms required to cause disease is not known, it is suspected to be very small. Meat becomes contaminated during slaughter, and organisms can be thoroughly mixed into beef when it is ground. Contaminated beef looks and smells normal. Other ways to transmit E. coli include: Person-to-person contact in families and in child-care and other institutional-care centers can also be places where the transmission of the bacteria can occur. Bacteria present on a cow's udders, or on equipment, may get into raw milk causing the infection. Infection may also occur after swimming in or drinking sewage-contaminated water. It has been confirmed that unpasteurized juices, such as apple cider, may also cause the infection. Bacteria in diarrhea stools of infected people can be passed from one person to another if hygiene or handwashing habits are inadequate. This is particularly likely among toddlers who are not toilet trained. Family members and playmates of these children are at high risk of becoming infected. Young children typically shed the organism in their feces for a week or two after their illness resolves.
Prevention	CDC recommendations for prevention of the infection include: Cook all ground beef or hamburger thoroughly. Make sure that the cooked meat is gray or brown throughout (not pink), any juices run clear, and the inside is hot. Using a digital instant-read meat thermometer, the temperature of the meat should reach a minimum of 160 degrees F. If you are served an undercooked hamburger in a restaurant, send it back. Consume only pasteurized milk and milk products. Avoid raw milk. Consume only pasteurized juices and ciders. Make sure that infected people, especially children, wash their hands carefully and frequently with soap to reduce the risk of spreading the infection. Drink municipal water that has been treated with adequate levels of chlorine, or other effective disinfectants. Avoid swallowing lake or pool water while swimming. Wash hands thoroughly after using the toilet. People with diarrhea should not: Swim in public pools or lakes Bathe with others Prepare food for others

	Salmonella
Description	Salmonella is a bacteria that infects the intestines and causes diarrhea, fever, and abdominal cramps 12 to 72 hours after infection. Over 1 million cases of salmonella infection are reported in the United States each year. The illness usually lasts four to seven days and most people recover without treatment. However, in some people the diarrhea may be so severe that the patient needs to be hospitalized. In those patients, the salmonella infection may spread from the intestines to the blood stream and then to other body sites and can cause death unless the person is treated promptly with antibiotics. Infants and those with impaired immune systems are more likely to have a severe illness.
Transmission	Salmonella may be spread by: Eating raw foods contaminated with animal feces. Contaminated foods usually look and smell normal. Contaminated foods are often of animal origin, such as beef, poultry, milk, or eggs, but all foods, including some unwashed fruits and vegetables, and peanut butter, may become contaminated. Many raw foods of animal origin are frequently contaminated, but fortunately, thorough cooking kills salmonella. Handling reptiles. Reptiles (such as iguanas and turtles) are particularly likely to harbor Salmonella and people should always wash their hands immediately after handling a reptile, even if the reptile is healthy. Adults should also be careful that children wash their hands after handling a reptile.
Prevention	Since foods of animal origin pose the greatest threat of salmonella contamination, do not eat raw or undercooked eggs, poultry, or meats. Remember that some sauces and desserts use raw eggs in their preparation, so be cautious of these, particularly in foreign countries. Also, follow these recommendations by the CDC: Make sure poultry and meat, including hamburgers, are well-cooked, not pink in the middle. Do not consume raw or unpasteurized milk or other dairy products. Thoroughly wash produce before eating it. Avoid cross-contamination of foods. Uncooked meats should be kept separate from produce, cooked foods, and ready-to-eat foods. All utensils, including cutting boards, knives, counters, etc., should be thoroughly washed after handling uncooked foods. Thoroughly wash hands before handling foods and between handling different food items. Thoroughly wash hands after contact with feces. Thoroughly wash hands after handling any reptiles, since reptiles are particularly likely to have Salmonella.

Viruses

	Rotavirus
Description	Rotavirus is the most common cause of severe diarrhea among children, resulting in the death of over 500,000 children annually worldwide. In the United States, the disease occurs most often in the winter, with annual epidemics occurring from December to June. The highest rates of illness occur among infants and young children, and most children in the United States are infected by 5 years of age. Adults can also be infected, though disease tends to be mild. The incubation period for rotavirus disease is approximately two days. The disease is characterized by vomiting and watery diarrhea for three to eight days, and fever and abdominal pain occur frequently. Immunity after infection is incomplete, but repeat infections tend to be less severe than the original infection.
Transmission	Rotavirus may be spread: Through accidentally swallowing the virus picked up from surfaces contaminated with stool from an infected person, such as toys, bathroom fixtures, changing tables, and diaper pails. Through ingestion of contaminated food, or contaminated water, such as the type of water found in a public swimming pool.
Prevention	A rotavirus vaccine that was approved by the FDA in 1998 was pulled from the market in 1999 because of an association between the vaccine and an increased risk for intussusception (form of bowel blockage) in infants aged one year or younger. However, no direct link was established to the vaccine as a cause of intussusception. A new rotavirus vaccine was approved by the FDA in 2006. The risk for intussusception with the new vaccine was evaluated in a large clinical trial of over 30,000 children, and no increased risk was found. The manufacturer of the vaccine will continue to closely monitor the vaccine's safety in additional clinical studies. Some, but not all, studies indicate there may be a very small risk of intussusception, but the benefits outweigh the possible risks and the CDC continues to recommend routine rotovirus vaccination of infants. Handwashing is a very important means of preventing the spread of rotavirus. Careful and frequent handwashing can prevent the spread of infection to other people. The CDC recommends: Adults should wash their hands after using the toilet, after helping a child use the toilet, after diapering a child, and before preparing, serving, or eating food. Children should wash their hands after using the toilet, after having their diapers changed (an adult should wash infant's or small child's hands), and before eating snacks or meals. Toys, bathrooms, and food preparation surfaces are disinfected frequently, especially if a sick child has been in the home. Use diapers with waterproof outer covers that can contain liquid stool or urine, or use plastic pants. Make sure that children wear clothes over diapers.

Parasites

	Giardia
Description	During the past 15 years, Giardia lamblia has become recognized as one of the most common waterborne diseases in humans in the United States. Giardia is a tiny parasite that lives in the intestines of people and animals. The parasite is passed in the bowel movement of an infected person or animal. It is found in every region of the United States and throughout the world. Diaper-aged children who attend day care centers, international travelers, hikers, campers, and others who drink untreated water from contaminated sources, are most at risk for developing infection with Giardia. Several community-wide outbreaks of infection have been linked to drinking municipal water contaminated with Giardia.
Transmission	People become infected after accidentally swallowing the parasite. Giardia may be found in soil, food, water, or on surfaces. Some of the ways people can become infected with Giardia include: Eating uncooked food contaminated with Giardia. Swallowing water from swimming pools, lakes, rivers, springs, ponds, or streams contaminated with sewage or feces from humans or animals. Accidentally swallowing the parasite picked up from surfaces contaminated with stool from an infected person, such as toys, bathroom fixtures, changing tables, diaper pails.
Prevention	The CDC recommends: Washing hands with soap and water after using the toilet, changing diapers, and before handling food. Washing and peeling all raw vegetables and fruits before eating. Avoiding drinking water from lakes, rivers, springs, ponds, or streams unless it has been filtered and chemically treated. Boiling drinking water for one minute to kill the Giardia parasite. This will ensure safe drinking water during community-wide outbreaks caused by contaminated drinking water. When camping or traveling in countries where the water supply may be unsafe, avoid drinking unboiled tap water and avoid uncooked foods washed with unboiled tap water. Bottled or canned carbonated beverages, seltzers, pasteurized fruit drinks, and steaming hot coffee and tea, are safe to drink. If your child has Giardia, avoid swimming in pools for two weeks after the diarrhea or loose stools have cleared. Giardia is fairly chlorine resistant and is passed in the stools of infected people for several weeks after they no longer have symptoms.

	Cryptosporidium
Description	Cryptosporidium, often referred to as "crypto," is a tiny parasite that can live in the intestines of humans and animals. The parasite is protected by an outer shell that allows it to survive outside the body for long periods of time and makes it very resistant to chlorine disinfection.
Transmission	Cryptosporidium may be spread by: Accidentally swallowing anything that has come in contact with the stool of a person or animal Swallowing contaminated water from swimming pools, hot tubs, lakes, rivers, springs, ponds, or streams contaminated with sewage or feces from humans or animals. Eating uncooked contaminated food. Picking cryptosporidium up from surfaces contaminated with stool from an infected person (such as toys, bathroom fixtures, changing tables, and diaper pails).
Prevention	The CDC recommends: Your child should wash their hands with soap and water after using the toilet, changing diapers, and before eating or helping prepare food. Avoid water or food that may be contaminated. Washing and/or peeling all raw vegetables and fruits before giving them to your child to eat. Avoiding drinking water from lakes, rivers, springs, ponds, or streams unless it has been filtered and chemically treated. Boiling drinking water for one minute to kill the cryptosporidium parasite. This will ensure safe drinking water during community-wide outbreaks caused by contaminated drinking water. When camping or traveling in countries where the water supply may be unsafe, avoid drinking unboiled tap water and avoid uncooked foods washed with unboiled tap water. Avoiding swimming in pools if your child has had cryptosporidium and for at least two weeks after diarrhea stops. Crypto can be passed in the stool and contaminate water for several weeks after your child no longer has symptoms. This has resulted in several outbreaks of cryptosporidium among pool users. Crypto can survive in chlorinated pools for several days.

Can my child get germs from food?

Almost everyone has experienced a foodborne illness at some point in time. Contrary to popular belief, foodborne illnesses can occur when food is prepared at a restaurant or at home. If food is handled and prepared safely, most illnesses can be avoided.

All food may contain some natural bacteria, and improper storage or handling gives the bacteria a chance to grow. Also, food can be contaminated with bacteria from other sources that can make you ill. Contaminated or unclean food can be very dangerous, especially to children. According to the CDC, each year foodborne illnesses kill 3,000 people of all ages. They also cause fever, stomach cramps, vomiting, and diarrhea in an estimated 48 million Americans.

Four major tips recommended by the CDC to prevent contaminating food

Use caution when buying food:
- When at the grocery store, pick up perishable food such as meat, eggs, and milk at the very end of your shopping, so they will stay cool.
- Take food home right away so that it does not spoil in a hot car.
- Avoid raw or unpasteurized milk.
- Because eggs, meat, seafood, and poultry are most likely to contain bacteria, do not allow their juices to drip on other food.
Store food properly:
- Store eggs, raw meat, poultry, and seafood in the refrigerator.
- A refrigerator should be set between 32 degrees F and 40 degrees F.
- A freezer should be set at or below 0 degrees F.
- Regularly clean and disinfect the refrigerator and freezer.
- Use containers to prevent contaminating other foods or kitchen surfaces. Do not store food uncovered in the refrigerator or freezer.
Use special precautions when preparing and cooking food:
- Wash your hands and clean and disinfect kitchen surfaces before, during, and after handling, cooking, and serving food.
- Defrost frozen food on a plate either in the refrigerator or in a microwave, but not on the counter.
- Cook food immediately after defrosting.
- Use different dishes and utensils for raw foods than you use for cooked foods.
- Wash raw fruits and vegetables before eating them.
Cool and promptly store leftovers after food has been served:
- Because harmful bacteria grow at room temperature, keep hot food hot and keep cold food cold. This is especially important during picnics and buffets.
- Do not leave perishable foods out for more than two hours.
- Promptly refrigerate or freeze leftovers in shallow containers or wrapped tightly in bags.
  
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  Gastroenteritis in Adults
  
  Gastroenteritis is an infection of the gut (intestines). It causes diarrhoea and may also cause you to be sick (vomit), and have tummy (abdominal) pain and other symptoms. In most cases the infection clears over several days but sometimes takes longer. The main risk is lack of fluid in the body (dehydration). The main treatment is to have lots to drink which aims to avoid dehydration. You should also eat as normally as possible. See a doctor if you suspect that you are dehydrating, or if you have any worrying symptoms such as those which are listed below.
  What is gastroenteritis and what causes it?
  Gastroenteritis is an infection of the gut (intestines). The severity can range from a mild tummy upset for a day or two with mild diarrhoea, to severe diarrhoea and being sick (vomiting) for several days or longer. Many germs (viruses, bacteria and other microbes) can cause gastroenteritis.
  A virus is the most common cause of gastroenteritis. For example, infection with noroviruses and adenoviruses are common causes of gastroenteritis in adults in the UK. However, other viruses can also be the cause. Viruses are easily spread from one person to another by close contact. This is often because of the virus being present on people's hands after they have been to the toilet. Surfaces or objects touched by the infected person can also allow transmission of the virus. The virus can also be passed on if the infected person prepares food. Outbreaks of a virus causing gastroenteritis in many people can occur - for example, in schools, hospitals or nursing homes.
  Food poisoning from eating food infected with microbes causes some cases of gastroenteritis. Many different types of microbes can cause food poisoning. Common examples are species of bacteria called Campylobacter, Salmonella and Escherichia coli (usually shortened to E. coli). Poisons (toxins) produced by bacteria can also cause food poisoning. Another group of microbes called parasites can also be a cause. Water contaminated by bacteria or other microbes is another common cause, particularly in countries with poor sanitation. See separate leaflet called Food Poisoning in Adults for further details.
  This is a general leaflet about gastroenteritis. There are also other leaflets that give more details about some of the different microbes that cause gastroenteritis.
  
  How common is gastroenteritis?
  Gastroenteritis is common. About 1 in 5 people in the UK will develop an episode of gastroenteritis in a year. Most people have a mild form of gastroenteritis and do not need to seek medical advice or to visit their doctor.
  
  What are the symptoms of gastroenteritis?
  - The main symptom is diarrhoea, often with being sick (vomiting) as well. Diarrhoea means loose or watery stools (faeces), usually at least three times in 24 hours. Blood or mucus can appear in the stools with some infections.
  - Crampy pains in your tummy (abdomen) are common. Pains may ease for a while each time you pass some diarrhoea.
  - A high temperature (fever), headache and aching limbs sometimes occur.
  If vomiting occurs, it often lasts only a day or so but sometimes longer. Diarrhoea often continues after the vomiting stops and commonly lasts for several days or more. Slightly loose stools may continue (persist) for a week or so further before a normal pattern returns. Sometimes the symptoms last longer.
  
  Symptoms of lack of fluid in the body (dehydration)
  Diarrhoea and vomiting may cause dehydration. Consult a doctor quickly if you suspect you 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 adults include:
  - Symptoms of severe dehydration in adults include:
  Dehydration in adults with gastroenteritis 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.
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  How is gastroenteritis diagnosed and do I need any tests?
  Most people with gastroenteritis recognise this from their typical symptoms and they do not usually need to see a doctor or to seek medical advice. Symptoms are often quite mild and commonly get better within a few days without any medical treatment.
  
  However, in some circumstances, you may need to see a doctor when you have gastroenteritis (see below about when to seek medical advice). The doctor may ask you questions about recent travel abroad, if you have been in contact with someone with similar symptoms, or if you have recently taken antibiotic medication or been admitted to hospital. This is to look for possible causes of your gastroenteritis. The doctor will also usually check you for signs of dehydration. They may check your temperature, pulse and blood pressure. They may also examine your tummy (abdomen) to look for any tenderness.
  
  Tests are not usually needed. However, if you are particularly unwell, have bloody stools (faeces), have recently travelled abroad, are admitted to hospital, or your symptoms are not getting better, your doctor may ask you to collect a stool sample. This can then be examined in the laboratory to look for the cause of the infection.
  
  When should I seek medical advice?
  Seek medical advice in any of the following situations, or if any other symptoms occur that you are concerned about:
  - If you suspect that you are becoming lacking in fluid in the body (dehydrated).
  - If you are being sick (vomiting) a lot and unable to keep fluids down.
  - If you have blood in your diarrhoea or vomit.
  - If you have severe tummy (abdominal) pain.
  - If you have severe symptoms, or if you feel that your condition is getting worse.
  - If you have a persisting high temperature (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.
  What is the treatment for gastroenteritis 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 fluid in the body (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 bout of diarrhoea (after each watery stool).
  - 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 advice of 200 mls after each bout of diarrhoea is in addition to this usual amount that you would drink.
  - If you have been sick (vomited), 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. 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. Home-made salt/sugar mixtures are used in developing countries if rehydration drinks are not available but they have to be made carefully, as too much salt can be dangerous. Rehydration drinks are cheap and readily available in the UK and are the best treatment.
  Anti-secretory medicines 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.
  
  Eat as normally as possible
  It used to be advised to not eat 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.
  
  Medication
  Antidiarrhoeal medicines are not usually necessary. However, you may wish to reduce the number of trips that you need to make to the toilet. You can buy antidiarrhoeal medicines from pharmacies. The safest and most effective is loperamide. The adult dose of this 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. It works by slowing down your gut's activity. You should not take loperamide for longer than five days.
  Note: do not give antidiarrhoeal medicines to children under 12 years. Also, do not use antidiarrhoeal medicines if you pass blood or mucus with the diarrhoea or if you have a high temperature. People with certain conditions should not take loperamide. Therefore, read the leaflet that comes with the medicine to be safe. For example, pregnant women should not take loperamide.
  Paracetamol or ibuprofen is useful to ease a high temperature (fever) or headache.
  As explained above, if symptoms are severe, or continue for more than several days, your doctor may ask for a sample of the diarrhoea. This is sent to the laboratory to look for infecting microbes (bacteria, parasites, etc). Sometimes an antibiotic or other treatments are needed if certain bacteria or other infections are found to be the cause. Antibiotics are not needed for gastroenteritis caused by viruses and may even make things worse.
  
  Are there any complications that can occur from gastroenteritis?
  Complications are uncommon in the UK. They are more likely in the very young, in pregnant women, or in the elderly. They are also more likely if you have an ongoing (chronic) condition such as diabetes or if your immune system may not be working fully. For example, if you are taking long-term steroid medication or you are having chemotherapy treatment for cancer.
  Possible complications include the following:
  - Lack of fluid (dehydration) and salt (electrolyte) imbalance in your body. This is the most common complication. It occurs if the water and salts that are lost in your stools (faeces), or when you have been sick (vomited), 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, kidney failure may also develop. Some people who become severely dehydrated need a drip of fluid directly into a vein. This requires admission to hospital.
  - Reactive complications. Rarely, other parts of the body may react to an infection that occurs in the gut (intestines). This can cause symptoms such as joint inflammation (arthritis), skin inflammation and eye inflammation (either conjunctivitis or uveitis). Reactive complications are uncommon when a virus causes gastroenteritis.
  - Spread of infection to other parts of your body such as your bones, joints, or the meninges that surround your brain and spinal cord. This is rare. If it does occur, it is more likely if gastroenteritis is caused by Salmonella spp. infection.
  - Persistent diarrhoea syndromes may rarely develop.
  - Irritable bowel syndrome is sometimes triggered by a bout of gastroenteritis.
  - Lactose intolerance can sometimes occur for a while after gastroenteritis. This is known as secondary or acquired lactose intolerance. Your 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 your body digest a sugar called lactose that is in milk. Lactose intolerance leads to bloating, tummy (abdominal) pain, wind and watery stools after drinking milk. The condition gets better when the infection is over and the gut lining heals. It is more common in children.
  - Haemolytic uraemic syndrome is another potential complication. It is rare and is usually associated with gastroenteritis caused by a certain type of E. coli infection. It is a serious condition where there is anaemia, a low platelet count in the blood and kidney failure. It is more common in children. If recognised and treated, most people recover well.
  - Reduced effectiveness of some medicines. During an 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 vomiting means that reduced amounts of the medicines are taken up (absorbed) into your body. Examples of such medicines are medicines 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.
  Preventing spread of infection to others
  Gastroenteritis can be easily passed on from person to person. If you have gastroenteritis, 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.
  - Don't share towels and flannels.
  - Don't prepare or serve food for others.
  - Regularly clean the toilets that you use, with disinfectant. Wipe the flush handle, toilet seat, bathroom taps, surfaces and door handles with hot water and detergent at least once a day. Keep a cloth just for cleaning the toilet (or use a disposable one each time).
  - Stay off work, college, etc, until at least 48 hours after the last episode of diarrhoea or being sick (vomiting).
  - Food handlers: if you work with food and develop diarrhoea or vomiting, you must immediately leave the food-handling area. For most, no other measures are needed, other than staying away from work until at least 48 hours after the last episode of diarrhoea or vomiting. Some special situations may arise and sometimes longer time off is needed. Specialist advice may be needed for some uncommon causes of gastroenteritis. If in doubt, seek advice from your employer or GP.
  - If the cause of gastroenteritis is known to be (or suspected to be) a microbe called Cryptosporidium spp., you should not swim in swimming pools for two weeks after the last episode of diarrhoea.
  Can gastroenteritis be prevented?
  The advice given in the previous section is mainly aimed at preventing the spread of infection to other people. However, even when we are not in contact with someone with gastroenteritis, proper storage, preparation and cooking of food and good hygiene help to prevent gastroenteritis.
  In particular, always wash your hands:
  - After you go to the toilet.
  - Before you touch food.
  - Between handling raw meat and food ready to be eaten. (There may be some germs (bacteria) on raw meat.)
  - After gardening.
  - After playing with pets (healthy animals can carry certain harmful bacteria).
  The simple measure of washing hands regularly and properly is known to make a big difference to the chance of developing gastroenteritis.
  You should also take extra measures when in countries of poor sanitation. For example, avoid water and other drinks that may not be safe and avoid food washed in unsafe water.