Gastroenteritis is an inflammation of the lining of the intestines caused by a virus, bacteria or parasites.

Viral gastroenteritis is inflammation of the lining of the stomach, small intestine, and large intestine. Several different viruses can cause viral gastroenteritis, which is highly contagious and extremely common. Viral gastroenteritis causes millions of cases of diarrhea each year. The most common problem with gastroenteritis is dehydration. This happens if you do not drink enough fluids to replace what you lose through vomiting and diarrhea.

Anyone can get viral gastroenteritis and most people recover without any complications, unless they become dehydrated.

Frequent hand-washing is one of the best ways to avoid getting sick and spreading illness. Hand-washing requires only soap and water or an alcohol-based hand sanitizer — a cleanser that doesn't require water.

Always wash your hands before:

  • Preparing food or eating
  • Treating wounds, giving medicine, or caring for a sick or injured person
  • Inserting or removing contact lenses

Always wash your hands after:

  • Preparing food, especially raw meat or poultry
  • Using the toilet or changing a diaper
  • Touching an animal or animal toys, leashes or waste
  • Blowing your nose, coughing or sneezing into your hands
  • Treating wounds or caring for a sick or injured person
  • Handling garbage, household or garden chemicals, or anything that could be contaminated — such as a cleaning cloth or soiled shoes
  • In addition, wash your hands whenever they look dirty.

The U.S. Food and Drug Administration has approved two vaccines to protect children from rotavirus infections: rotavirus vaccine, live, oral, pentavalent (RotaTeq); and rotavirus vaccine, live, oral (Rotarix). RotaTeq is given to infants in three doses at 2, 4, and 6 months of age. Rotarix is given in two doses. The first dose is given when the infant is 6 weeks old, and the second is given at least 4 weeks later but before the infant is 24 weeks old.

Parents of infants should discuss rotavirus vaccination with a health care provider.

People who may be more susceptible to gastroenteritis include:

  • Young children.

     Children in child care centers or elementary schools may be especially vulnerable because it takes time for a child's immune system to mature. 
  • Older adults.

     Adult immune systems tend to become less efficient later in life. Older adults in nursing homes, in particular, are vulnerable because their immune systems weaken and they live in close contact with others who may pass along germs.
  • Schoolchildren, churchgoers or dormitory residents.

     Anywhere that groups of people come together in close quarters can be an environment for an intestinal infection to get passed.
  • Anyone with a weakened immune system.

     If your resistance to infection is low — for instance, if your immune system is compromised by HIV/AIDS, chemotherapy or another medical condition — you may be especially at risk.

Each gastrointestinal virus has a season when it's most active. If you live in the Northern Hemisphere, for instance, you're more likely to have rotavirus or norovirus infections between October and April.

Four types of viruses cause most cases of viral gastroenteritis.


Rotavirus is the leading cause of gastroenteritis among infants and young children. Rotavirus infections are most common in infants 3 to 15 months old. Symptoms usually appear 1 to 3 days after exposure. Rotavirus typically causes vomiting and watery diarrhea for 3 to 7 days, along with fever and abdominal pain. Rotavirus can also infect adults who are in close contact with infected children, but the symptoms in adults are milder.


Caliciviruses cause infection in people of all ages. Norovirus is the most common calicivirus  and the most common cause of viral gastroenteritis in adults. Norovirus is usually responsible for epidemics of viral gastroenteritis. Norovirus outbreaks occur all year but are more frequent from October to April. People infected with norovirus typically experience nausea, vomiting, diarrhea, abdominal cramps, fatigue, headache and muscle aches. The symptoms usually appear 1 to 2 days after exposure to the virus and last for 1 to 3 days.


Adenovirus mainly infects children younger than 2 years old. Of the 49 types of adenoviruses, one strain affects the gastrointestinal tract, causing vomiting and diarrhea. Symptoms typically appear 8 to 10 days after exposure and last 5 to 12 days. Adenovirus infections occur year-round.


Astrovirus primarily infects infants and young children, but adults may also be infected. This virus causes vomiting and watery diarrhea. Symptoms usually appear 3 to 4 days after exposure and last 2 to 7 days. The symptoms are milder than the symptoms of norovirus or rotavirus infections. Infections occur year-round, but the virus is most active during the winter months.

The main symptoms of viral gastroenteritis are

  • watery diarrhea

  • vomiting

Other symptoms include

  • headache

  • fever

  • chills

  • abdominal pain

Symptoms usually appear within 12 to 48 hours after exposure to a gastroenteritis-causing virus and last for 1 to 3 days. Some viruses cause symptoms that last longer.

Viral gastroenteritis is usually diagnosed based on symptoms alone. People who have symptoms that are severe or last for more than a few days may want to see a health care provider for additional tests. A health care provider may ask for a stool sample to test for rotavirus or norovirus or to rule out bacteria or parasites as the cause of the gastroenteritis.

During an epidemic of viral gastroenteritis, health care providers or public health officials may test stool samples to find out which virus is responsible for the outbreak.

Most cases of viral gastroenteritis resolve over time without specific treatment. Antibiotics are not effective against viral infections. The primary goal of treatment is to reduce symptoms and prevent complications.

Over-the-counter medicines such as loperamide (Imodium) and bismuth subsalicylate (Pepto-Bismol) can help relieve symptoms in adults. These medicines are not recommended for children.