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Gastroenteritis or Gastric Flu or Tummy Bug or Gastro: Definition, Types, Epidemiology, Pathophysiology, Causes, Symptoms, Signs, Treatment, Investigations

What is Gastroenteritis?

Gastroenteritis is irritation and inflammation of the gastrointestinal tract that involves the stomach and the small intestines. Gastroenteritis generally results in acute diarrhea.

The severity of gastroenteritis mainly depends on an individual’s immune system’s ability to fight with the infection. Electrolytes and fluids may be lost due to vomiting and diarrhea. Many people recover easily by drinking fluids and going back to a normal diet, but recovery may not be easy in infants and elderly people sometimes leading to life-threatening illness unless fluids are restored and condition is treated.

 Gastroenteritis or Gastric Flu or Tummy Bug or Gastro

Gastroenteritis is also known as gastric flu, tummy bug, and gastro.

Classification and Types of Gastroenteritis or Gastric Flu or Tummy Bug or Gastro

Gastroenteritis Can Be Classified Into Different Categories Based On The Cause Of The Infection:

  • Viral Gastroenteritis: Viral gastroenteritis is highly contagious in nature and is most common form of gastroenteritis. It could spread with close interaction with infected people, contaminated food, contaminated water, the sharing of eating utensils, poor hygiene habits, the elderly living in nursing homes, students living in student halls and even children in nurseries and preschools all may be at higher risk of developing viral gastroenteritis due to the close proximity in which they breathe and interact. This virus is truly responsible for the infection and could easily spread through the air or through close contact.
  • Bacterial Gastroenteritis: Bacterial gastroenteritis is uncommon and generally very serious in nature. The infection in bacterial gastroenteritis could spread through poor hygiene habits, contact with infected people, the sharing of eating utensils, contaminated water and contaminated food. The reason behind parasitic infections could spread through a contact with infected human or animal wastes, drinking of contaminated water and ingestion of raw seafood.
  • Eosinophilic Gastroenteritis: Eosinophilic gastroenteritis is also quite less common. Both adults and young children could be affected with it. The signs of this gastroenteritis are inclusion of other organs in the body aside from the gastrointestinal tract, lack of known cause for eosinophilia, and pain in the abdomen.
  • Cryptosporidiosis Gastroenteritis: Cryptosporidiosis gastroenteritis is caused by the parasite named Cryptosporidium. The reason behind Cryptosporidiosis could be the parasites taken in by mouth through infected water and food, or from individual to individual or animal to individual. This disease is mild, but can seriously affect the individuals with weak immune system. Major sources of cryptosporidiosis could be contaminated water supplies, public swimming pools and child care centers.

Epidemiology of Gastroenteritis or Gastric Flu or Tummy Bug or Gastro

Rotavirus in children under the age of 5 causes about 110 million cases of gastroenteritis worldwide every year and nearly half a million deaths. Another significant viral agent which causes gastroenteritis is adenovirus. Of these, about 82% deaths occur in the world’s poorest countries.

The incidence in the developed countries is about 1 to 2.5 cases per child per year and this has been a major cause for hospitalization. The most important factors are age, hygiene, living conditions and cultural habits. Most cases of gastroenteritis occur during summer in the tropics and in the temperate climates during winter.

Pathophysiology of Gastroenteritis or Gastric Flu or Tummy Bug or Gastro

There are different bacterial species that cause gastroenteritis and they will act on the gastrointestinal system in different ways.

There are bacteria, which enter the gastrointestinal tract and attach themselves to the intestinal mucosa or lining where they begin to secrete toxins. These bacteria do not attack intestinal mucosa cells. The toxins secreted by them have an impact on nutrient absorption leading to malabsorption and cause the mucosal cells to secrete electrolytes and water. This will be seen as profuse watery diarrhea with vomiting that generally starts within 12 to 48 hours of ingestion.

There are other bacteria that attack the mucosal cells causing bleeding and ulceration. This leads to inflammatory diarrhea, which is coupled with bloody diarrhea sometimes and the patient also has significant abdominal pain.

This gastrointestinal inflammation and irritation causes the typical signs and symptoms like fever, nausea, vomiting, abdominal pain, and diarrhea that are seen in cases of bacterial gastroenteritis.

Causes and Risk Factors of Gastroenteritis or Gastric Flu or Tummy Bug or Gastro

The main cause of gastroenteritis is bacteria and virus that again are the most common forms of infection. These infectious agents can enter the gastrointestinal tract from outside the body through contaminated food or water, or can grow internally from some abnormal condition within.

Gastroenteritis caused by viruses are milder than those caused by bacteria and may last up to a day or two, but bacterial gastroenteritis can last for up to a week or more.

Bacteria: Given Below Are Most Common Bacteria That Cause Gastroenteritis:

  • Salmonella – Typhoid fever, handling reptiles such as turtles or poultry that carry the germs.
  • Escherichia coli – Traveler’s diarrhea, dysentery, colitis, food poisoning, or uremic syndrome.
  • Shigella – Dysentery.
  • Campylobacter – Unpasteurized milk, undercooked meat.

Virus: The most common reason for getting infected with virus is poor handwashing habits. Given below are most common viruses that cause gastroenteritis:

  • Adenoviruses.
  • Astroviruses.
  • Caliciviruses.
  • Norovirus.
  • Rotaviruses.

Parasites: The most common reason for getting infected with parasites is contaminated water, most commonly through swimming pools. Given below are most common parasites that cause gastroenteritis:

  • Giardia.
  • Cryptosporidium.

Other Causes: Food allergies, heavy metals, certain chemical toxins often found in seafood, antibiotics, and other medications may also be responsible for bouts of gastroenteritis though these may not be infectious to others. Few of the common causes are:

  • Exposure to heavy metals like mercury, arsenic, and lead.
  • Medications like aspirin.
  • Antibiotics.
  • Nonsteroidal anti-inflammatory drugs.
  • Steroids.
  • Laxatives.
  • Caffeine.
  • Lactose intolerance in milk and milk products such as cheese and ice cream.

Signs and Symptoms of Gastroenteritis or Gastric Flu or Tummy Bug or Gastro

Gastroenteritis symptoms may generally result in stomach spasms or pain, diarrhea or vomiting, with inflammatory infections of the colon or noninflammatory infection of the upper small bowel.

The Symptoms Of Gastroenteritis May Include

  • Headaches.
  • Loss of appetite.
  • Abnormal flatulence.
  • Nausea and vomiting.
  • Abdominal pain.
  • Weakness and Fainting.
  • Abdominal cramps.
  • Bloody stools.
  • Diarrhea.

The Major Factors Include

  • Bacterial colitis which may cause blood stained diarrhea.
  • Poor feeding habits in infants leading to frequent watery stools caused with viral diarrhea. There are certain cases where bile can be vomited when the stomach is empty.

Children With Gastroenteritis May Have Symptoms Like

  • Running a low fever.
  • Lack of sleep.
  • Signs of dehydration which include dry mucous membranes.
  • Lethargic.
  • Skin turgor reduces.
  • Tachycardia.
  • Discoloration of skin.
  • Sunken fontanelles.
  • Darkened eye circles.
  • Sunken eyeballs.
  • Glassy eyes.
  • Poor perfusion and shock.

Treatment of Gastroenteritis or Gastric Flu or Tummy Bug or Gastro

  • Drinking fluids may help to avoid dehydration and relieve the symptoms. Fluid replacement helps in correcting electrolyte imbalance, which in turn may aid to stop vomiting.
  • Children should be given rehydration solutions through oral route such as Rehydrate, Pedialyte, Resol, and Rice-Lyte.
  • Fruit juice, tea, cola and sports drinks may not be able to replace fluid or electrolytes lost from vomiting or diarrhea correctly nor will the plain water. Intestines irritated due to gastroenteritis do not even absorb plain water quite well, also that fact that plain water will not aid in replacing electrolytes.
  • Following each loose stool, children less than two years of age should be given one to three ounces of rehydration solution. Older children should drink as much as three to eight ounces of rehydration solution and adults as much as possible.
  • In regions where pediatric drinks are not available, a common homemade recipe for rehydration is being used where two tablespoons of sugar mixed with a quarter teaspoon of table salt and quarter teaspoon of baking soda or table salt is mixed in 1 liter of clean or already boiled water.
  • After 24 hours, bland diet should be started with BRAT diet i.e., bananas, rice, applesauce without sugar, toast, pasta, or potatoes.
  • For adults, initial intake of ice chips and clear, nondairy, noncaffeinated liquids such as fruit juices, ginger ale, Gatorade, and Kool-Aid or other commercial drink mixes. A soft bland diet such as the BRAT diet may be started after successful 24 hours of fluid diet without vomiting.
  • Medical Treatment: If the patient is not able to take fluids by mouth because of vomiting, an IV may be inserted to restore fluids back into the body for rehydration. A surgeon, toxicologist, gastroenterologist, or other specialist’s evaluation may be required for severe symptoms.
  • Antibiotics are generally not given until a specific bacteria has been identified as using wrong antibiotics can worsen some of the infections or prolong their life.

Investigations for Gastroenteritis or Gastric Flu or Tummy Bug or Gastro

Simple gastroenteritis is easy to diagnose with just the symptoms and there are no specific diagnostic tests required.

If the symptoms like fever, diarrhea, and bloody stool are persistent for two weeks or more then examination of stool for Clostridium difficile is advised. Also blood cultures are recommended to identify if bacteria such as Shigella, Salmonella, Campylobacter and Enterotoxic Escherichia coli are the causes of the disease.

Microscopy for parasites, ova and cysts may also be helpful.


  1. Kosek, M., Bern, C., & Guerrant, R. L. (2003). The global burden of diarrhoeal disease, as estimated from studies published between 1992 and 2000. Bulletin of the World Health Organization, 81(3), 197-204.

  2. Guerrant, R. L., Van Gilder, T., Steiner, T. S., Thielman, N. M., Slutsker, L., Tauxe, R. V., … & Griffin, P. M. (2001). Practice guidelines for the management of infectious diarrhea. Clinical Infectious Diseases, 32(3), 331-351.

Team PainAssist
Team PainAssist
Written, Edited or Reviewed By: Team PainAssist, Pain Assist Inc. This article does not provide medical advice. See disclaimer
Last Modified On:August 16, 2023

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