Gastroenteritis: Protecting Your GI Tract from Infection

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man with gastroenteritis

Gastroenteritis (or called stomach flu) is an inflammation of the lining of the gastrointestinal tract commonly caused by viral, bacterial or parasitic infections. Anyone can be affected by gastroenteritis, which causes diarrhea, abdominal pain, and vomiting. Read more to keep you and your family away from gastroenteritis!


What is Gastroenteritis? Causes and types of Gastroenteritis

Gastroenteritis is the inflammation and irritation of the lining of the stomach and intestines. It is mainly caused by infections of various pathogens.

Viral gastroenteritis

Viral infection is a more common cause of gastroenteritis. The viruses could spread through contaminated water, food, or surfaces. Some examples of these viruses include:

  • Norovirus: This virus is a very common cause of gastroenteritis which affects people of all ages and occurs at any time of the year. You can get infected by having food or liquids that are contaminated, touching contaminated surfaces, or having direct contact with an infected person. Norovirus is also widespread in crowded places. Symptoms usually last for 1-3 days.
  • Rotavirus: Rotavirus is one of the most common causes of gastroenteritis among infants and children worldwide. The virus is primarily transmitted by fecal-oral route, while contaminated water, food, surfaces are also possible. Symptoms usually last for 3-8 days. 
  • Adenovirus: Adenovirus mainly affects children and spreads through droplets from sneezing or coughing. Symptoms may last for 1-2 weeks. 

Bacterial gastroenteritis

Bacterial gastroenteritis can be easily transmitted from people with poor hygiene. By not washing their hands, they can contaminate foods and surfaces which you then touch and contract the bacteria. Common types of bacteria include: 

  • Salmonella: You usually get the bacteria via undercooked eggs, poultry, and meat. An infected person may also spread the bacteria to other people or surfaces by not washing their hands properly. 
  • Escherichia coli (E. coli): This bacteria can be found in animal faeces and commonly spread through contaminated water, undercooked beef and unpasteurized milk. 
  • Campylobacter: Campylobacter can be contracted through raw or undercooked meat, unpasteurized milk, and contaminated water. You can also get this from not washing hands after handling infected animals. 
  • Shigella: Shigella is found in the stool of infected people and spreads through contaminated water and surfaces. It can also be found in swimming pools. Symptoms usually last for 5-7 days.
  • Others: Staphylococcus aureus, Clostridium perfringens, Vibrio cholerae, etc. are other bacteria contributing to gastroenteritis.

Parasitic gastroenteritis

Gastroenteritis caused by parasitic infection is uncommon in developed cities. They usually spread through fecal-oral routes. Parasites that can cause gastroenteritis include:

  • Giardia duodenalis
  • Cryptosporidium
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Signs and Symptoms of Gastroenteritis

Signs and symptoms of gastroenteritis vary, depending on the causes and severity. In general, common gastroenteritis symptoms include:

  • Nausea
  • Vomiting
  • Bloody diarrhea (can be caused by some types of bacteria)
  • Nonbloody diarrhea ( can be caused by some types of virus and bacteria)
  • Abdominal cramps and pain
  • Fever and chills
  • Headache
  • Loss of appetite

For viral gastroenteritis, symptoms usually appear 1-2 days after the infection and get better within 1-3 days, whereas the symptoms of bacterial gastroenteritis typically develop 1-5 days after the infection. 


If your symptoms do not improve (e.g. vomiting for more than 1-2 days, or diarrhea that continues for more than several days) or you have bloody diarrhea, high fever, dizziness or no urine output, you should seek medical help immediately. For infants and children who have persistent vomiting for several hours, sunken eyes, or crying without tears, seek medical attention promptly. 

Risk factors of Gastroenteritis

Gastroenteritis can affect anyone at any age and at any time, but the following conditions can increase the risk:

  • Age: Infants and children are at higher risk because of their immature immune systems, while the elderly are more likely to develop gastroenteritis due to their weakened immune systems. 
  • Weaken immune system: Anyone with a weakened immune system (e.g. due to HIV/AIDS or cancer) is more susceptible to infections. 
  • Living in crowded areas: A crowded space favors the transmission of pathogens, such as norovirus. 
  • Traveling: There is a chance that foods and water may be contaminated in some developing countries. 

Complications of Gastroenteritis

The main complication of gastroenteritis is dehydration and electrolyte imbalance. It happens when you lose too much water and electrolytes by vomiting and diarrhea. Therefore, it is important to intake adequate amounts of water during gastroenteritis to prevent dehydration and restore electrolyte balance. As long as you drink enough to replace fluids you lose from vomiting and diarrhea, mild dehydration usually is not a problem. Common dehydration symptoms include: 

  • Fatigue
  • Dizziness and lightheadedness
  • Confusion
  • Dry mouth
  • Dark-colored urine
  • Decreased urine output
  • Sunken eyes or sunken fontanel in infants or young children
  • No tears when crying in infants

If these symptoms do not improve after drinking plenty of fluids, or you have persistent diarrhea and vomiting, you should seek medical attention immediately because severe dehydration may require intravenous treatment in the hospital. If dehydration is left untreated, it could lead to coma, hypovolemic shock or kidney failure. 

Diagnosis of Gastroenteritis

Diagnosis of gastroenteritis can be simply done by medical history and physical examination of your signs and symptoms. Your doctor might take a stool sample or order blood tests in severe cases.

Treatments of Gastroenteritis

Gastroenteritis usually clears up within a week, depending on the type of infection. Therefore, the aims of treatment are mainly preventing dehydration and relieving signs and symptoms. Treatment options of gastroenteritis include: 

  • Antibiotics: For severe cases of bacterial gastroenteritis, antibiotics might be prescribed. However, you should not take antibiotics on your own without a diagnosis because antibiotics are not effective against viruses and parasites. Improper use of antibiotics can also lead to drug resistance. 
  • Oral rehydration solutions (ORS): To prevent dehydration, it is vital to replace salts and water you lose in vomiting and diarrhea. ORS products are available over-the-counter, commonly as powder or sachet. Be careful not to use sports drinks as a means for rehydration because these products contain high levels of sugar which may worsen the condition. 
  • Intravenous fluid replacement: In severe cases, you might need to be hospitalized to receive intravenous therapy.
  • Other medications: If you experience fever or abdominal pain, paracetamol would be helpful. Seldomly, you might be prescribed ondansetron to reduce vomiting. 

Home remedies for Gastroenteritis

To prevent dehydration and ease your symptoms, some at-home care strategies are recommended:

  • Get plenty of rest and fluids
  • Try to eat small amounts of food: Once your stomach starts to feel better, it is recommended to ease back into eating food in small amounts.
  • Foods to eat and avoid: Try to have a bland diet when you restart eating. Foods like rice, bread and apple are easier to digest. Avoid foods that can worsen your condition, such as spicy foods, sugary foods, high-fat foods, fruit juices and dairy products.
  • Be careful with medications: Avoid taking nonsteroidal anti-inflammatory drugs (e.g. ibuprofen, naproxen) for symptomatic relief because these medicines may make your stomach more upset. Besides, do not give aspirin to children or teenagers because it can cause a rare but serious side effect (Reye’s syndrome). Please consult your doctor or pharmacist before taking any over-the-counter medications.

Prevention of Gastroenteritis

Gastroenteritis is highly contagious. To prevent getting infected, the following steps can lower the risk:

  • Wash your hands regularly: Wash your hands thoroughly with soap and water before handling foods and eating, as well as after using the toilet and touching animals. You should also teach your children to do so. Also, you can use hand sanitizer outdoors whenever soap and water are not available. 
  • Wash fruits and vegetables and cook foods thoroughly: Proper handling of foods can avoid contracting most of the pathogens.
  • Take precautions when traveling: There is a risk you can get infected from contaminated foods and drinks. Avoid ice cubes, raw and undercooked foods. Use bottled water whenever possible. 
  • Avoid close contact: Avoid contact with others who have gastroenteritis symptoms such as vomiting or diarrhea. 


How long does it take to get over gastroenteritis?

It really depends on which pathogen causes it. In general, gastroenteritis would get better within 1-3 days, while it can also last for a week or longer. If you have vomiting for more than 1-2 days or diarrhea that lasts for more than several days, you should seek medical help immediately.

What are the main symptoms of gastroenteritis?
How do you get gastroenteritis?
What should you eat when you have gastroenteritis?

This article is medically reviewed by Dr. Ernest Han Fai Li. Dr. Li is a specialist in gastroenterology and hepatology practicing at the Central Gastroenterology & Hepatology Center currently. Dr. Li served in the public hospital for 12 years after his graduation from the Chinese University of Hong Kong in 2004. At the same time, Dr. Li is a medical consultant to the Hong Kong Fire Service Officers Association, a medical advisor to the Board of Chung Shak-Hei (Cheung Chau) Home for the Aged and the chairperson of the District 303 Lions Club Organ Donation Committee.

This article was independently written by Healthy Matters and is not sponsored. It is informative only and not intended to be a substitute for professional medical advice, diagnosis or treatment. It should not be relied upon for specific medical advice.

Dr. Li Han Fai Ernest
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