Gastroenteritis means inflammation of the stomach and small and large intestines. Viral gastroenteritis is an infection caused by a variety of viruses and results in vomiting or diarrhea.

It is often called the “stomach flu,” although it is not caused by the influenza viruses.

What causes viral gastroenteritis?

Many different viruses can cause gastroenteritis, including:

• Rotaviruses
• Adenoviruses
• Caliciviruses
• Astroviruses
• Norwalk virus
• A group of Noroviruses

Although the symptoms may be similar viral gastroenteritis is not caused by:

• Bacteria (such as Salmonella or Escherichia coli)
• Parasites (such as Giardia)
• Medications
• Other medical conditions

Your doctor can determine if the diarrhea is caused by a virus or by something else.

What are the symptoms of viral gastroenteritis?

The main symptoms of viral gastroenteritis are:

• Watery diarrhea
• Vomiting

The affected person may also have:

• Headache
• Fever
• Abdominal cramps (“stomach ache”)

In general, the symptoms begin 1 to 2 days following infection with a virus that causes gastroenteritis and may last for 1 to 10 days, depending on which virus causes the illness.

Is viral gastroenteritis a serious illness?

For most people, it is not. People who get viral gastroenteritis almost always recover completely without any long-term problems.

Gastroenteritis is a serious illness, however, for people who are unable to drink enough fluids to replace what they lose through vomiting or diarrhea.

Those at risk for dehydration from loss of fluids include:

• Infants
• Young children
• The disabled or elderly

Immune compromised people are at risk for dehydration because they may get a more serious illness, with greater vomiting or diarrhea. They may need to be hospitalized for treatment to correct or prevent dehydration.

Is the illness contagious? How are these viruses spread?

Yes, viral gastroenteritis is contagious.

The viruses that cause gastroenteritis are spread through close contact with infected people (for example, by sharing food, water, or eating utensils). Individuals may also become infected by eating or drinking contaminated foods or beverages.

How does food get contaminated by gastroenteritis viruses?

• Food may be contaminated by food preparers or handlers who have viral gastroenteritis, especially if they do not wash their hands regularly after using the bathroom.
• Shellfish may be contaminated by sewage, and people who eat raw or undercooked shellfish harvested from contaminated waters may get diarrhea.
• Drinking water can also be contaminated by sewage and be a source of spread of these viruses.

Where and when does viral gastroenteritis occur?

Viral gastroenteritis affects people in all parts of the world. Each virus has its own seasonal activity.

For example, in the United States, rotavirus and astrovirus infections occur during the cooler months of the year (October to April), whereas adenovirus infections occur throughout the year.

Viral gastroenteritis outbreaks can occur in institutional settings, such as:

• Schools
• Child care facilities
• Nursing homes

Viral gastroenteritis can also occur in other group settings, such as:

• Banquet halls
• Cruise ships
• Dormitories
• Campgrounds

Who gets viral gastroenteritis?

Anyone can get it. Viral gastroenteritis occurs in people of all ages and backgrounds. However, some viruses tend to cause diarrheal disease primarily among people in specific age groups.

• Rotavirus infection is the most common cause of diarrhea in infants and young children under 5 years old.
• Adenoviruses and astroviruses cause diarrhea mostly in young children, but older children and adults can also be affected.
• Norwalk and Noroviruses are more likely to cause diarrhea in older children and adults.

How is viral gastroenteritis diagnosed?

Generally, viral gastroenteritis is diagnosed by a doctor on the basis of the symptoms and medical examination of the patient.

Rotavirus infection can be diagnosed by laboratory testing of a stool specimen. Tests to detect other viruses that cause gastroenteritis are not in routine use.

How is viral gastroenteritis treated?

The most important part of treating viral gastroenteritis in children and adults is to prevent severe loss of fluids (dehydration). This treatment should begin at home. Your doctor may give you specific instructions about what kinds of fluid to give.

CDC recommends that families with infants and young children keep a supply of oral rehydration solution (ORS) at home at all times and use the solution when diarrhea first occurs in the child. ORS is available at pharmacies without a prescription. Follow the written directions on the ORS package, and use clean or boiled water.

Medications, including antibiotics (which have no effect on viruses) and other treatments, should be avoided unless specifically recommended by a doctor.

Can viral gastroenteritis be prevented?

Yes. People can reduce their chance of getting infected by:

• Frequent hand washing
• Prompt disinfection of contaminated surfaces with household chlorine bleach-based cleaners
• Prompt washing of soiled articles of clothing
• Avoid food or water that is thought to be contaminated

Is there a vaccine for viral gastroenteritis?

There is no vaccine or medicine currently available that prevents viral gastroenteritis. A vaccine is being developed, however, that protects against severe diarrhea from rotavirus infection in infants and young children.