Symptoms & Causes of Viral Gastroenteritis (“Stomach Flu”)

What are the symptoms of viral gastroenteritis?

The symptoms of viral gastroenteritis include

What are the symptoms of dehydration?

Symptoms of dehydration, the most common complication of viral gastroenteritis, may include the following in adults

  • extreme thirst and dry mouth
  • urinating less than usual
  • feeling tired
  • dark-colored urine
  • decreased skin turgor, meaning that when a person’s skin is pinched and released, the skin does not flatten back to normal right away
  • sunken eyes or cheeks
  • light-headedness or fainting

If you are the parent or caretaker of an infant or young child with viral gastroenteritis, you should watch for the following signs of dehydration

  • thirst
  • urinating less than usual, or no wet diapers for 3 hours or more
  • lack of energy
  • dry mouth
  • no tears when crying
  • decreased skin turgor
  • sunken eyes or cheeks

Seek care right away

In most cases, viral gastroenteritis is not harmful. However, viral gastroenteritis can become dangerous if it leads to dehydration. Anyone with signs or symptoms of dehydration should see a doctor right away. A person with severe dehydration may need treatment at a hospital.

Viral gastroenteritis symptoms may be similar to the symptoms of other health problems. Certain symptoms may suggest that a person has a different health problem.

The symptoms listed below may suggest that an adult or child has a severe case of viral gastroenteritis, dehydration, or a more serious health problem instead of viral gastroenteritis.

Adults

Adults with any of the following symptoms should see a doctor right away

  • change in mental state, such as irritability or lack of energy
  • diarrhea lasting more than 2 days
  • high fever
  • vomiting often
  • six or more loose stools in a day
  • severe pain in the abdomen or rectum
  • stools that are black and tarry or contain blood or pus
  • symptoms of dehydration

Adults should also see a doctor if they aren’t able to drink enough liquids or oral rehydration solutions—such as Pedialyte, Naturalyte, Infalyte, and CeraLyte—to prevent dehydration or if they do not improve after drinking oral rehydration solutions.

Older adults, pregnant women, and adults with a weakened immune system or another health condition should also see a doctor right away if they have any symptoms of viral gastroenteritis.

Infants and children

If an infant or child has signs or symptoms of viral gastroenteritis, don’t hesitate to call a doctor for advice. Diarrhea is especially dangerous in newborns and infants, leading to severe dehydration in just a day or two. A child with symptoms of dehydration can die within a day if left untreated.

If you are the parent or caretaker of an infant or child with any of the following signs or symptoms, seek a doctor’s help right away

  • change in the child’s mental state, such as irritability or lack of energy
  • diarrhea lasting more than a day
  • any fever in infants
  • high fever in older children
  • frequent loose stools
  • vomiting often
  • severe pain in the abdomen or rectum
  • signs or symptoms of dehydration
  • stools that are black and tarry or contain blood or pus

You should also seek a doctor’s help right away if a child has signs or symptoms of viral gastroenteritis and the child is an infant, was born prematurely, or has a history of other medical conditions. Also seek a doctor’s help right away if the child is not able to drink enough liquids or oral rehydration solutions to prevent dehydration or if the child does not improve after drinking oral rehydration solutions.

Parents sitting with a sick boy and calling a doctor.
If a child has signs or symptoms of a viral gastroenteritis, don’t hesitate to call a doctor for advice.

What kinds of viruses cause viral gastroenteritis?

Many different viruses can cause viral gastroenteritis. The most common causes of viral gastroenteritis include

  • norovirus. Norovirus is the most common cause of viral gastroenteritis. Symptoms usually begin 12 to 48 hours after you come into contact with the virus and last 1 to 3 days.2
  • rotavirus. Symptoms usually begin about 2 days after you come into contact with the virus and last for 3 to 8 days.3 Vaccines can prevent rotavirus infection.
  • adenovirus. Symptoms typically begin 3 to 10 days after you come into contact with the virus and last 1 to 2 weeks.4
  • astrovirus. Symptoms typically begin 4 to 5 days after you come into contact with the virus and last 1 to 4 days.5,6

Norovirus causes infections in people of all ages. Rotavirus, adenovirus, and astrovirus most often infect infants and young children, but they can also infect adults.

Viruses may cause viral gastroenteritis any time of the year. In the United States, norovirus, rotavirus, and astrovirus are more likely to cause infections in the winter.

Do flu viruses cause viral gastroenteritis (“stomach flu”)?

Although some people call viral gastroenteritis “stomach flu,” influenza (flu) viruses do not cause viral gastroenteritis. Flu viruses cause infections of the respiratory system, while viral gastroenteritis is an infection of the intestines.

Are viruses the only cause of gastroenteritis?

No. While viruses cause viral gastroenteritis, bacteria, parasites, and chemicals may cause other kinds of gastroenteritis.

When gastroenteritis is caused by consuming foods or drinks contaminated with viruses, bacteria, parasites, or chemicals, this is called food poisoning.

How does viral gastroenteritis spread?

Viral gastroenteritis spreads from person to person through contact with an infected person’s stool or vomit.

If you have viral gastroenteritis, viruses will be present in your stool and vomit. You may spread the virus in small bits of stool or vomit, especially if you don’t wash your hands thoroughly after using the bathroom and

  • touch surfaces or objects used by other people
  • prepare or serve foods and drinks for other people
  • shake hands with or touch another person

Infected people who do not have symptoms can still spread viruses. For example, norovirus may be found in your stool before you have symptoms and up to 2 weeks after you recover.2

Norovirus is especially contagious, meaning that it spreads easily from person to person. Norovirus can live for months on surfaces such as countertops and changing tables. When an infected person vomits, the virus may become airborne and land on surfaces or on another person.

Viral gastroenteritis may spread in households, day care centers and schools, nursing homes, cruise ships, restaurants, and other places where people gather in groups.

If water comes into contact with stools of infected people, the water may become contaminated with a virus. The contaminated water can spread the virus to foods or drinks, and people who consume these foods or drinks may become infected. People who swim in contaminated water may also become infected.

References

May 2018
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This content is provided as a service of the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), part of the National Institutes of Health. The NIDDK translates and disseminates research findings through its clearinghouses and education programs to increase knowledge and understanding about health and disease among patients, health professionals, and the public. Content produced by the NIDDK is carefully reviewed by NIDDK scientists and other experts.