Viral gastroenteritis is an intestinal infection caused by several different, highly infectious viruses.
The main symptoms of viral gastroenteritis are watery diarrhea and vomiting. Other symptoms are headache, fever, chills, and abdominal pain. Symptoms usually appear within 4 to 48 hours after exposure to the virus and last for 1 to 2 days, though symptoms can last as long as 10 days. Viral gastroenteritis causes millions of cases of diarrhea each year.
The viruses that cause viral gastroenteritis damage the cells in the lining of the small intestine. As a result, fluids leak from the cells into the intestine and produce watery diarrhea.
Although sometimes called "stomach flu," viral gastroenteritis is not caused by the influenza virus and does not affect the stomach.
Anyone can get viral gastroenteritis through unwashed hands, close contact with an infected person, or food and beverages that contain the virus.
Viral gastroenteritis has no specific treatment. Antibiotics are not effective against viruses. Treatment focuses on reducing the symptoms and preventing dehydration.
Most people recover without any complications. However, viral gastroenteritis can be serious when people cannot drink enough fluids to replace what is lost through vomiting and diarrhea—especially infants, young children, the elderly, and people with weak immune systems.
Four types of viruses cause most viral gastroenteritis.
Rotavirus is the leading cause among children 3 to 15 months old and the most common cause of diarrhea in children under the age of 5 years. Symptoms of rotavirus infection appear 1 to 2 days after exposure. Rotavirus typically causes vomiting and watery diarrhea for 3 to 8 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.
Rotavirus infections in the U.S. are most common from November to April.
Calcivirus (including Norovirus)
Caliciviruses cause infection in people of all ages. This family of viruses is divided into 4 types, the noroviruses being the most common and most responsible for infecting people. (Noroviruses have also been refered to as the Norwalk virus. Infected people experience vomiting and diarrhea, fatigue, headache, and sometimes muscle aches. The symptoms appear within 1 to 3 days of exposure.
Norovirus infections are usually responsible for epidemics of viral gastroenteritis and occur more frequently from October to April.
Adenovirus occurs mainly in children under the age of 2 years. Of the 49 types of adenoviruses, one strain affects the gastrointestinal tract causing vomiting and diarrhea. Symptoms typically appear 1 week after exposure.
Adenovirus infections occur year round.
Astrovirus also infects primarily infants, young children, and the elderly. This virus is most active during the winter months. Vomiting and diarrhea appear within 1 to 3 days of exposure.
How is Viral Gastroenteritis Transmitted?
Viral gastroenteritis is highly contagious. The viruses are commonly transmitted by people with unwashed hands. People can get the viruses through close contact with infected individuals by sharing their food, drink, or eating utensils, or by eating food or drinking beverages that are contaminated with the virus. Noroviruses in particular, are typically spread to other people by contact with stool or vomit of infected people and through contaminated water or food—especially oysters from contaminated waters.
People who no longer have symptoms may still be contagious, since the virus can be found in their stool for up to 2 weeks after they recover from their illness. Also, people can become infected without having symptoms and they can still spread the infection.
Outbreaks of viral gastroenteritis can occur in households, child care settings, schools, nursing homes, cruise ships, camps, dormitories, restaurants, and other places where people gather in groups. If you suspect that you were exposed to a virus in one of these settings or by foods prepared on the premise of places such as a restaurant, deli, or bakery, you may want to contact your local health department, which tracks outbreaks.
Diagnosis of Viral Gastroenteritis
If you think you have viral gastroenteritis, you may want to see your doctor. Doctors generally diagnose viral gastroenteritis based on the symptoms and a physical examination. Your doctor may ask for a stool sample to test for rotavirus or to rule out bacteria or parasites as the cause of your symptoms. No routine tests are currently available for the other types of viruses.
Treatment of Viral Gastroenteritis
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 the symptoms, and prompt treatment may be needed to prevent dehydration.
Your body needs fluids to function. Dehydration is the loss of fluids from the body. Important salts or minerals, known as electrolytes, can also be lost with the fluids. Dehydration can be caused by diarrhea, vomiting, excessive urination, excessive sweating, or by not drinking enough fluids because of nausea, difficulty swallowing, or loss of appetite.
In viral gastroenteritis, the combination of diarrhea and vomiting can cause dehydration. The symptoms of dehydration are:
- Excessive thirst
- Dry mouth
- Little or no urine or dark yellow urine
- Decreased tears
- Severe weakness or lethargy
- Dizziness or lightheadedness
If you notice any of these symptoms, you should talk to your doctor. Mild dehydration can be treated by drinking liquids. Severe dehydration may require intravenous fluids and hospitalization. Untreated severe dehydration can be life threatening.
Children present special concerns. Because of their smaller body size, infants and children are at greater risk of dehydration from diarrhea and vomiting. Oral rehydration solutions, such as Pedialyte, can replace lost fluids, minerals, and salts.
The following steps may help relieve the symptoms of viral gastroenteritis:
- Allow your gastrointestinal tract to settle by not eating for a few hours.
- Sip small amounts of clear liquids or suck on ice chips if vomiting is still a problem.
- Give infants and children oral rehydration solutions to replace fluids and lost electrolytes.
- Gradually reintroduce food, starting with bland, easy-to-digest food, like toast, broth, apples, bananas, and rice.
- Avoid dairy products, caffeine, and alcohol until recovery is complete.
- Get plenty of rest.
Prevention of Viral Gastroenteritis
Prevention is the best way to avoid viral gastroenteritis by following the tips listed below. No vaccine is available for viral gastroenteritis with the exception of a rotavirus vaccine.
Otherwise, you can avoid infection by:
- Washing your hands thoroughly for 20 seconds after using the bathroom or changing diapers
- Washing your hands thoroughly for 20 seconds before eating
- Disinfecting contaminated surfaces such as countertops and baby changing stations
- Not eating or drinking foods or liquids that might be contaminated