Gastroenteritis (Stomach Flu)

Acute gastroenteritis lasts about seven to 14 days while chronic may last for months or longer.

Gastroenteritis is a nonspecific term for various inflammatory problems in the gastrointestinal tract with the most common symptoms and signs being diarrhea, nausea, vomiting, and abdominal pains. Gastroenteritis is often referred to as the "stomach flu," but it is not related to the influenza virus.

In the U.S., less than 2% of the estimated 100 million people with stomach flu symptoms yearly require hospitalization. Still, in developing countries, it is a leading cause of death, mainly due to dehydration.

Although the stomach flu and food poisoning share some common symptoms such as diarrhea, nausea and vomiting, stomach cramps, and muscle aches, they are not the same condition.

• Stomach flu or gastroenteritis means any nonspecific inflammatory problem in the gastrointestinal tract; some doctors consider the stomach flu to be more narrowly defined as a viral infection that attacks the digestive system.
• Food poisoning specifically is caused by eating or drinking contaminated food or fluid that contains bacteria, viruses, parasites, and/or the toxins they produce.

Consequently, there is some crossover between the two terms.

In addition:

• Food poisoning usually is found in small outbreaks that occur among individuals that have ingested the same foods or drink, and symptoms occur rapidly within hours; whereas the stomach flu has a more gradual onset of symptoms and usually lasts longer than food poisoning.
• Food poisoning usually requires ingesting the poison and does not easily spread to other individuals; whereas, stomach flu is highly contagious and can be spread quickly to other individuals.

Although both the stomach flu and the flu (influenza) may be caused by viruses, the viral genus and species are different for each entity.

• The viruses that cause the majority of stomach flu (gastroenteritis) are Norovirus spp; whereas the viruses that cause influenza are mainly Influenza A and B viral spp and subtypes.
• Stomach flu results mainly in problems with the gastrointestinal tract while influenza (flu) involves the respiratory tract.

Infectious agents such as bacteria and viruses are the most frequent causes of gastroenteritis in the U.S. and worldwide. Infections cause diarrhea and other symptoms by causing inflammation of the gastrointestinal (GI) tissue. The infections increase the fluid content in the intestines and colon by changing the gastrointestinal tract's ability to absorb water and by increasing the speed of transit (motility) for things you ingest. This, in turn, causes diarrhea. Infectious agents may physically damage intestinal cells directly or indirectly with secreted toxins.

Viral causes of stomach flu

The most prevalent cause of gastroenteritis in the U.S. and the world is Norovirus. It causes about 50%-70% of viral gastroenteritis cases, while Rotavirus, Astrovirus, Adenovirus, and Sapovirus strains cause most of the other viral gastroenteritis infections. Norovirus also was listed as the leading cause of gastroenteritis in children under 5 years old according to the Centers for Disease Control and Prevention (CDC).

Bacterial causes of stomach flu

Bacterial causes of gastroenteritis that occur worldwide are Salmonella, Shigella, Campylobacter Aeromonas, and Escherichia coli (E. coli) strains of bacteria. Other bacteria like Clostridium, Vibrio, Campylobacter, and Yersinia spp can cause outbreaks occasionally. Occasionally, some bacterial causes of gastroenteritis (for example, Salmonella and certain E. coli strains) may produce hemorrhagic or bloody diarrhea.

Parasitic causes of stomach flu

Parasites such as Giardia, Cryptosporidium, and Entamoeba infections can cause gastroenteritis, and occasionally, other parasites have outbreaks such as the Cyclospora outbreak that occurred from 2012 to 2013 in the U.S.

Other causes of stomach flu

There are many other less frequent causes of gastroenteritis such as food allergies (eosinophilic gastroenteritis), antibiotics, and toxins. Gastroenteritis symptoms are possible side effects of many medicines.

How does food become contaminated with gastroenteritis-causing bacteria or viruses?

In most instances, food and drinks come into contact with feces contaminated with the infecting agent. This can happen in the fields, or transport, storage, and processing of food and drinks. In processed foods and drinks, this contamination is relatively rare, but when it occurs, an outbreak of the disease is often traced back to faulty equipment, human errors in the processing, and/or a breakdown of quality-control procedures.

The large majority of causes (viral and bacterial) of gastroenteritis are contagious, usually through food or water contamination. In addition, they can be transferred from person to person. Exposures to body fluids (for example, feces or droplets containing infectious agents) are common sources that transmit the disease to others (See transmission section).

A few causes of gastroenteritis are not contagious, for example, food allergies or the side effects of medications.

Most viral and bacterial causes of stomach flu can be transferred to other people by direct and indirect contact, usually by the fecal-oral route.

• Direct contact could involve an infant's hand touching feces-contaminated surfaces and then touching a sibling or relative; indirect contact would be touching a doorknob or railing on a cruise ship or in a dorm that is contaminated and a person touches the contaminated surface and transferring the agent by touching their mouth.
• Another common way to get stomach flu is by drinking or eating contaminated foods and liquids.

Gastroenteritis (stomach flu) is a common, worldwide disease and almost everyone suffers from it a few times in their life because it is almost impossible to avoid contact with some of the viral and bacterial causes.

• People living in crowded conditions (military, cruise ships, dorms) are at higher risk, as are people living in developing countries who often have a diet that contains contaminated food or water.
• Infants, children, and some adults (elderly, immunosuppressed) are at higher risk because of immature or depressed immune systems and also because they can become dehydrated faster than older children and adults.
• Some people taking antibiotics are at higher risk because the antibiotics depress the normal GI microbes and allow bacteria or viruses like Clostridium difficile to predominate and cause disease.
• People who do not practice good hygiene and hand-washing techniques are at higher risk, as are those who eat undercooked and/or unwashed foods or drink from potentially contaminated fluid sources (rivers, streams, unpasteurized milk, for example).

The signs and symptoms of stomach flu may vary depending on the cause.

• The primary symptom of viral gastroenteritis (stomach flu) is diarrhea (non-bloody).
• Nausea, vomiting, and some abdominal cramping may accompany the diarrhea.
• Mild fever (about 100 F or 37.77 C), chills, head, and muscle, and tiredness may occur in some individuals with viral gastroenteritis.
• Vomiting is occasional.
• Symptoms usually last about two to five days and then begin to resolve with viral gastroenteritis.
• Bacterial gastroenteritis (stomach flu) shares many symptoms of viral stomach flu, but in some individuals, bacteria may cause bloody diarrhea (hemorrhagic gastroenteritis).

Similar symptoms may also be seen with other causes of stomach flu (drugs, food allergies, toxins), and symptoms may include:

• Abdominal pain
• Weight loss
• Muscle aches and pains
• Headache
• Eosinophilia (mainly in allergic gastroenteritis)
• Electrolyte loss
• Severe gastroenteritis means the person has signs of dehydration; this is a medical emergency

Children with gastroenteritis or stomach flu usually have diarrhea, but may have other symptoms such as:

• Refusing to eat or drink or being very thirsty
• Either increased or low or no urine output
• Weight loss
• Lethargy
• Bloody diarrhea
• Pinched skin that does not rapidly return to normal is a sign of dehydration and decreased fluid intake

Most individuals with viral or mild bacterial-caused gastroenteritis require no treatment or can be treated by the patient's primary care provider or pediatrician. For patients with more severe gastroenteritis, infectious disease specialists, gastroenterologists, emergency medicine specialists, allergists, critical care physicians, and hematologists may be consulted.

If gastroenteritis symptoms last more than five days, increase in severity (fever of 101 F or 38.33 C or higher), or the person develops bloody diarrhea, dehydration, constant abdominal pain, or other symptoms, see a physician. The patient may have some gastroenteritis symptoms but may have a disease more serious than self-limiting gastroenteritis. Signs and symptoms of dehydration may include decreased or no urine production, dry mucus membranes, dry mouth or skin, no tears, weakness, lightheadedness, and low blood pressure, while children may show little or no urination, become lethargic, have skin that "tents up" when pinched. Signs of dehydration in anyone are good reasons to see a doctor immediately.

There are no specific tests for gastroenteritis, thus gastroenteritis is most often diagnosed by the symptoms it produces, mainly diarrhea. Because gastroenteritis is usually a self-limited disease, the large majority of people are never seen or diagnosed by a doctor. However, during outbreaks like those seen on cruise ships, viral and bacterial cultures or polymerase chain reaction (PCR) and other immunologically based tests can eventually identify the causative pathogen. By the time this identification occurs, most individuals with gastroenteritis have begun to recover.

When gastroenteritis symptoms become severe, most public health officials and health care professionals run such tests to identify the causative agent of a specific disease, based on the history of the patients, physical exams, and symptoms. In addition, patients with similar histories of recent food or drink they had in common with others often help to discover the source of the disease (for example, people who got diarrhea had salads from the same food source).

Most people with the stomach flu require no formal treatment. The key to a rapid and safe recovery at home (home remedy) is proper hydration. If dehydration occurs, the patient should be evaluated by a doctor. Healthcare professionals may choose to begin IV fluids, the treatment of choice for rapid rehydration.

Other medications may be prescribed to reduce the symptoms of gastroenteritis. To reduce vomiting, promethazine (Phenergan), prochlorperazine (Compazine), or ondansetron (Zofran) are often used. Healthcare providers may prescribe diphenoxylate and atropine (Lomotil) or lopermadine (Imodium) to slow diarrhea. In most mild cases, doctors recommend no medical treatment for gastroenteritis symptoms as all of the drugs have side effects and if the patient stays well hydrated, the symptoms usually stop soon anyway.

As gastroenteritis symptoms abate, especially vomiting, doctors may recommend a BRAT diet (bananas, rice, apples, and toast) for a day or two before returning to the patient's regular diet. Potatoes, lean meat such as chicken, and whole grains can help replace nutrients and electrolytes lost with diarrhea.

Patients who have more serious symptoms or other symptoms in addition to gastroenteritis need to be evaluated, diagnosed, and treated by a physician because the patient will likely have a specific disease that will need treatment. The treatment will depend on the cause of the illness (for example, salmonellosis or Clostridium difficile toxin). Antibiotics and other treatments may not be recommended for some of these diseases so an accurate diagnosis of the disease is important. For Clostridium difficile-infected patients, antibiotic sensitivity testing may need to be done to determine the most effective antibiotics to use.

Many different natural and/or home remedies may help reduce gastroenteritis symptoms:

• Home treatment consists of adequate fluid intake so dehydration is prevented
• Clear fluids are recommended (Pedialyte especially for young children, Gatorade, PowerAde, and other sports drinks), but not fruit juices or milk as they may prolong the symptoms
• Salt
• Ginger
• Baking soda
• Apple cider vinegar
• Basil
• Chamomile tea
• Asafetida spice
• Zinc
• Cinnamon
• Mint
• Turmeric
• Yogurt

If dehydration occurs, the patient should be immediately evaluated by a doctor. Discuss home remedies with your physician before using them.

Some healthcare professionals suggest a special diet for gastroenteritis, especially for viral and/or bacterial infections in children. First and foremost is adequate fluid rehydration to prevent dehydration.

The diet frequently suggested is termed the "BRAT" diet (bananas, rice, applesauce, and toast). These foods are not usually irritating but are soothing for the gastrointestinal tract. Although some doctors think this diet may not markedly benefit patients, others recommend it for both adults and children for a day or two to make the transition from the resolving symptoms of acute gastroenteritis to the patient's previously normal diet.

The prognosis (outlook) for complete recovery is excellent in most people infected with viral and bacterial-caused gastroenteritis, as long as the person keeps well hydrated. Because infants, children, pregnant women, and adults who are elderly or immunosuppressed usually dehydrate faster than healthy adults and sometimes are more difficult to rehydrate orally, their prognosis can range from excellent to poor. Their prognosis depends on how dehydrated they become and how effective the attempts to rehydrate the patient are.

The prognosis for those patients who develop gastroenteritis symptoms as part of a specific disease process (for example, shigellosis) varies from good to poor, depending on the severity of the specific disease process.

Depending upon the cause of gastroenteritis, it may be considered acute or chronic.

• Acute gastroenteritis (viral) lasts about seven to 14 days and is then usually self-cured.
• Chronic gastroenteritis (for example, allergic gastroenteritis) may last for months or longer if not diagnosed and appropriately treated.

Most patients who get gastroenteritis have no complications and will completely recover. The major complication for some patients is dehydration; infants, children, the elderly, and immunosuppressed are at higher risk for this complication. In many third-world countries, hydration of infants is difficult at best so there are many infant deaths worldwide due to dehydration caused by gastroenteritis.

No diet will prevent gastroenteritis but food preparation plays a strong role in preventing gastroenteritis. In general, there are some actions people can do to prevent or reduce the chance of getting gastroenteritis, including:

• Hand washing, especially before eating and after any close association with an infected person or items (clothing, bedding, toys) they have touched
• Launder items daily that infected persons wear
• Avoid direct contact with infected individuals when possible
• Do not eat undercooked foods, especially meats
• Do not eat raw foods or drink untreated water
• Do not drink untreated or unpasteurized fluids, especially milk
• Thoroughly wash any produce, especially in third-world countries, before eating
• While traveling, avoid all raw foods and ice; drink only from sealed bottled products and use bottled water for tooth brushing

There is a vaccine available against rotavirus that has reduced this infection in children. Also, there is a vaccine available against cholera-causing bacteria (Vibrio), but it is not widely available. A clinical trial of a Norovirus vaccine was done with some success. It is likely commercial vaccines against some causes will be available shortly.