Written by Ada’s Medical Knowledge Team
What is viral gastroenteritis?
Viral gastroenteritis is a type of gastroenteritis – a common condition sometimes called stomach flu or food poisoning. Gastroenteritis is the result of irritation and inflammation in the stomach and intestines. It can be caused by infection with a virus such as rotavirus, bacteria or parasites, among other things. When caused by a virus, it is called viral gastroenteritis. While it can be very unpleasant, most cases of viral gastroenteritis can be treated at home, and clear up within a few days without causing complications. 1 2
Symptoms of viral gastroenteritis can range from mild to severe and vary among people. However, the main symptoms are typically vomiting and mild fever, which develop quickly, followed by watery diarrhea for a few days. 3
Feeling unwell? Get a symptom assessment with the free Ada app. Or find out more about how our symptom checker works before you try it for yourself.
Viral gastroenteritis can be caused by a number of different types of viruses, including rotavirus, norovirus and adenovirus. 3 The viruses can be transmitted direct from one person to another or spread through contaminated food and water. Depending on the source of infection, a large group of people may develop viral gastroenteritis at the same time, e.g. an outbreak on a cruise ship or at a summer camp. 4
Treatment for viral gastroenteritis typically involves: 4 1
- Resting at home
- Drinking plenty of fluids to avoid dehydration
- When necessary, taking medication to relieve nausea and diarrhea
In some cases, when a person is not able to keep fluids down and is becoming dehydrated, replacement of fluids through an intravenous (IV) drip at a hospital may be necessary. Antibiotics are not helpful for viral gastroenteritis.
Generally, people make a full recovery, and a bout of viral gastroenteritis does not cause any complications. However, if it occurs in a person with a weakened immune system, someone who is pregnant, very young or elderly, or someone with a chronic condition such as diabetes, viral gastroenteritis can be serious, and medical advice should be sought without delay. In addition, anyone experiencing severe symptoms should see a doctor immediately. Furthermore, if symptoms are mild but do not improve within a few days, or where a person has recently returned from travel abroad, medical advice should be sought. 4 1
Viral gastroenteritis can affect adults and children (see pediatric viral gastroenteritis) of all ages. It is very contagious and can be spread easily. For this reason, it is important for people who have viral gastroenteritis to take steps to avoid passing it on to others, such as practicing good personal hygiene and avoiding the preparation of food for other people. In general, the following can help to reduce the likelihood of developing gastroenteritis: 1 3 5
- Washing one’s hands well after using the toilet
- Taking precautions to ensure food is prepared, cooked and stored properly
- Avoiding consumption of inadequately-treated or untreated water
- Having babies vaccinated against rotavirus
Symptoms of viral gastroenteritis
The main signs and symptoms of viral gastroenteritis include: 6 4 3 7 8 9
- Nausea and/or vomiting
- Watery diarrhea; mucus and blood are not usually present
Other symptoms may include: 6 4 3 7 8 9
- Abdominal (belly) pain
- Low-grade fever
- Muscle aches
Symptoms may be mild or more severe and may vary depending on the particular virus. They tend to develop quickly. Worried you may have gastroenteritis? Start a free symptom assessment now.
If symptoms are severe or do not begin to improve within 2-3 days, it is important to contact a doctor without delay. Furthermore, medical attention should be sought immediately if:
- There are any indications of serious dehydration, such as passing little to no urine or dizziness that does not go away
- There is blood, pus or a black color in the diarrhea
- There is constant vomiting that makes it impossible to keep down fluids
- There is very intense abdominal pain
- There is a fever over 38 degrees Celsius (101 F), in adults or children
In addition, a doctor should be contacted urgently if the affected person:
- Has recently returned from overseas travel
- Is pregnant
- Is a very young child
- Is an elderly person
- Has a weakened immune system
- Has a chronic condition such as inflammatory bowel disease, Crohn’s disease or diabetes
Causes of viral gastroenteritis
Viral gastroenteritis can be caused by many different viruses, including: 3 8
The viruses can be transmitted easily from one person to another through close contact, for example by touching a person with viral gastroenteritis and then touching one’s mouth, or sharing food, cutlery or towels with the person. Another route of transmission is touching a contaminated surface or object, such as a doorknob, counter or changing table and then touching one’s mouth. Infection can also occur through the consumption of contaminated food and drinks, such as in the case of: 6 10 7 8 9
- Unhygienic food preparation, e.g. a cook not washing their hands after going to the toilet
- Inadequately-treated drinking water
Diagnosis of viral gastroenteritis
When symptoms are mild, a diagnosis of viral gastroenteritis can often be made without seeing a doctor, and the condition can be treated at home. 1 However, if there is any uncertainty or concern over the condition or symptoms are severe, seeing a doctor is very important.
A doctor will take the person’s medical history and perform a physical examination, taking care to rule out other common gastrointestinal conditions such as gastritis. In most cases, it will not be necessary to order tests to confirm the diagnosis of gastroenteritis. However, in cases that are severe or long lasting, a doctor may request blood and/or stool tests to investigate.
Viral gastroenteritis treatment
Most cases of viral gastroenteritis clear up without specific medical treatment. 8 As long as symptoms are not severe and there are no signs of dehydration, a person can generally treat viral gastroenteritis in an adult or child at home.
The following home remedies and over-the-counter treatment approaches are recommended for mild cases of viral gastroenteritis: 4 1 7 8 9
- Bed rest
- Consuming plenty of fluids in the form of water or oral rehydration drinks; at the very least, small sips should be taken between being sick or having bowel movements
- Eating light meals when appetite returns; plain foods like bread and rice may be helpful
- Taking an antidiarrheal medication, e.g. loperamide, only when necessary and there is no fever, and no blood or mucus is present in the stool
- Taking antiemetic (anti-nausea) medication for nausea and vomiting, when necessary
- Taking probiotics may slightly shorten the duration of diarrhea
If a person is unable to keep any fluids down or shows signs of dehydration (see below), they may need to be treated with an IV drip at a hospital.
Good to know: Antibiotics are not prescribed for viral gastroenteritis, as they are not effective against viruses. Antibiotics are only effective against bacteria. In a severe case of bacterial gastroenteritis, a course of antibiotics may be recommended.
Complications of viral gastroenteritis
In most cases, an episode of viral gastroenteritis clears up completely, without causing any long-term problems or complications. 6 However, in a few cases, there may be complications. The risk of developing complications from viral gastroenteritis is highest in very young children, elderly people and people who have a chronic condition such as diabetes, or a weakened immune system. 1 7
Dehydration is the most common complication of viral gastroenteritis. 1 9
Signs and symptoms of dehydration in adults include: 11
- Muscle cramps
- Urinating less and dark-colored urine
- Dry mouth
- Eyes appearing sunken in the head
In addition to the above, signs of dehydration in children can include: 11
- Drowsiness or irritability
- Increased heart rate
- Fewer wet nappies
- No tears when crying
If signs and symptoms of dehydration do not go away with the replacement of lost fluids or if a person is unable to keep fluids down, a doctor should be seen immediately. Dehydration can be extremely serious for both children and adults.
Other possible complications of viral gastroenteritis include: 1 5
- Reduced effectiveness of medications, e.g. birth control pills or diabetes medicine
- Temporary intolerance to lactose, the sugar in cow’s milk
- Irritable bowel syndrome
Rare complications from viral gastroenteritis include: 1 5
- Reactive inflammation in other parts of the body, causing conditions like reactive arthritis
- Persistent diarrhea
- Bleeding in the gastrointestinal tract 12
- Guillain-Barre syndrome, a serious condition in which the body’s immune system mistakenly attacks the nerves
Prevention of viral gastroenteritis
Good personal and food hygiene, as well as the use of water from clean, adequately-treated sources only, can help to reduce a person’s risk of developing viral gastroenteritis.
Practicing good hygiene
The following general precautions are recommended: 6 10 13 1
- Always wash your hands well with soap and water or use an alcohol-based hand sanitizer after using the toilet
- Always wash your hands well before preparing food
- Wash fruit and vegetables in clean water before using them
- Cook food thoroughly
- Regularly clean kitchen work surfaces with a disinfectant
- When traveling to other countries, drink only bottled water or water that has been boiled for at least 10 minutes, and only eat food that has been well cooked and fruit that can be peeled
If you have viral gastroenteritis, doing the following can help to prevent its spread: 6 10 1
- Wash your hands well with soap and water or use an alcohol-based hand sanitizer after using the toilet
- Clean the toilet and bathroom thoroughly with disinfectant on a daily basis
- Avoid sharing cutlery, towels, clothing and linen, also wash your items separately in hot water, with bleach if possible
- Avoid preparing food for other people for at least two days after the vomiting or diarrhea has cleared up
- Stay off work or school, if possible, until at least two days after the vomiting or diarrhea has cleared up
- Avoid swimming for two weeks after the vomiting or diarrhea has cleared up
Vaccinations for viral gastroenteritis
Viral gastroenteritis in infants can be very serious. To reduce the likelihood of it occurring, it is possible for babies to receive a course of rotavirus vaccinations. These injections are generally considered to be safe and effective against most strains of rotavirus and form part of the recommended infant vaccination schedule in some countries. 4 14 15 16 17
Viral gastroenteritis FAQs
Q: Is viral gastroenteritis contagious?
A: Yes. Viral gastroenteritis is contagious. It can be spread from one person to another in the following ways:
- Close contact with someone who has viral gastroenteritis, e.g. sharing food, drinks, utensils, kissing
- Touching a surface that has been contaminated by someone with viral gastroenteritis and then touching your mouth
It can also be spread via contaminated food and water. 6 10
Q: Bacterial vs. viral gastroenteritis: what are the differences?
A: Bacterial gastroenteritis is caused by bacteria, e.g. Campylobacter, Salmonella and Escherichia coli, while viral gastroenteritis is caused by viruses, e.g. norovirus and rotavirus. Viruses are the more common cause of gastroenteritis in the USA and most other parts of the developed world. Both types of gastroenteritis cause inflammation and irritation in the digestive tract. In most cases of gastroenteritis, identifying whether the cause is viral or bacterial is not necessary, as the symptoms are similar, and the treatment methods are largely the same. 4
Q: What is the best diet for viral gastroenteritis?
A: There is no specific diet that is recommended for viral gastroenteritis. It is very important to replace fluids to avoid dehydration, but the stomach can be allowed to settle before reintroducing small portions of food. Suggestions for what to eat while recovering include:
- Clear broths and soups
- Bland, simple foods such as rice, plain crackers, bananas and toast; some people recommend the “BRAT” diet, which stands for bananas, rice, applesauce and toast, 18 for a day or two
- Later, lean meat, fish and vegetables – all cooked
It is recommended that dairy products and rich, spicy, or fatty foods be avoided until the person is feeling substantially better. Caffeine and alcohol should also be avoided. 19 20 21
Q: How long does stomach flu last?
A: Viral gastroenteritis typically clears up within 1-3 days. However, sometimes it can last longer, with a duration of up to 10 days. If vomiting does not stop within two days, diarrhea does not start to improve within three days, or there are signs of dehydration, it is important to see a doctor. 20 13 22
Q: Can viral gastroenteritis last for weeks?
A: Gastroenteritis typically does not last for weeks. Most cases of viral gastroenteritis, as well as bacterial gastroenteritis clear up within a few days. If symptoms persist, it may be a sign of severe infection or a different condition, and medical advice should be sought. You can also try using the Ada app to find out more about your symptoms.
Q: Can viral gastroenteritis recur?
A: It is possible to be infected by a stomach virus more than once, though the same virus does not usually come back very soon after an infection. Many people experience more than one bout of viral gastroenteritis in their adult lives, and younger children commonly experience more than one episode in the space of a year (read about viral gastroenteritis in children). 2 3 If you have recently experienced gastroenteritis and the symptoms seem to have returned, it is advisable to see a doctor to check for other conditions.
Q: Can viral gastroenteritis cause blood in the stool?
A: Viral gastroenteritis does not usually cause blood in the stool, or feces. If you notice blood in your stool (poo), it may be a sign of a different, serious type of bacterial gastroenteritis or another condition, and a doctor should be seen without delay. If there is blood in your vomit, a doctor should also be seen without delay. 20 1
Q: Can viral gastroenteritis cause appendicitis?
A: Viral gastroenteritis is not thought to be a cause of appendicitis. However, symptoms of appendicitis may sometimes be mistaken for gastroenteritis.
Other names for viral gastroenteritis
- Stomach flu, gastric flu
- Stomach bug, tummy bug
- Stomach virus
- Food poisoning
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