Viral Gastroenteritis

Gastroenteritis means inflammation of the stomach and small and large intestines. Viral gastroenteritis is an infection caused by a number of viruses that results in vomiting or diarrhea. It is often called the "stomach flu," although it is not caused by the influenza viruses. Highly contagious, viral gastroenteritis is the second most common illness in the United States. It causes millions of cases of diarrhea each year.

Image of the digestive system, esophagus, gallbladder, liver, stomach, sigmoid colon, duodenum, pancreas, colon, small intestine, anus, rectum. Source: NIDDK

Symptoms

Anyone can get viral gastroenteritis and most people recover without any complications. However, viral gastroenteritis can be serious when people are not able to drink enough fluids to replace what is lost through vomiting and diarrhea. The people most vulnerable to dehydration include infants, young children, the elderly, and people with weak immune systems.

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 one to two days, though symptoms can last as long as ten days.

Causes

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. Four types of viruses cause most viral gastroenteritis.

Rotavirus particles visualized by immune electron microscopy in stool filtrate from child with acute gastroenteritis. 70-nm particles possess distinctive double-shelled outer capsid. Bar = 100 nm. Source: CDC^[1]

• Rotavirus is the leading cause among children three to fifteen months old and is the most common cause of diarrhea in children under the age of five years. Symptoms of rotavirus infection appear one to two days after exposure. Rotavirus typically causes vomiting and watery diarrhea for three to eight 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. In the United States, rotavirus infections are most common from November to April.

• Adenovirus occurs mainly in children under the age of two years. Of the 49 types of adenoviruses, two serotypes (40 and 41) cause gastroenteritis.^[2] Symptoms typically appear one week after exposure. Adenovirus infections occur year round.

• Caliciviruses cause infection in people of all ages. This family of viruses is divided into four types, the noroviruses being the most common and most responsible for infecting people. The noroviruses are usually responsible for epidemics of viral gastroenteritis and occur more frequently from October to April. Infected people experience vomiting and diarrhea, fatigue, headache, and sometimes muscle aches. The symptoms appear within one to three days of exposure.

• Astrovirus also infects primarily infants, young children, and the elderly. This virus is most active during the winter months. Vomiting and diarrhea appear within one to three days of exposure.

Viral gastroenteritis is often mistakenly called “stomach flu,” but it is not caused by the influenza virus. Also, viral gastroenteritis is not caused by bacteria or parasites. For information about bacterial infections, please see the Foodborne Illness.

Diagnosis

In most cases, gastroenteritis is diagnosed based on the symptoms. Laboratory tests may be performed on a stool sample to test for rotavirus or to rule out bacteria or parasites as the cause. Public health labs may use advanced polymerase chain reaction (PCR) tests to determine the cause of a large outbreak. No routine tests are currently available for the other types of viruses.

Treatment

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.

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

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 for 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.

• Allowing the gastrointestinal tract to settle by not eating for a few hours.
• Sipping small amounts of clear liquids or sucking on ice chips if vomiting is still a problem.
• Giving infants and children oral rehydration solutions to replace fluids and lost electrolytes.
• Gradually reintroducing food, starting with bland, easy-to-digest food, like toast, broth, apples, bananas, and rice.
• Avoiding dairy products, caffeine, and alcohol until recovery is complete.
• Getting plenty of rest.

Prevention

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 newly released rotavirus vaccine called Rotateq. The oral vaccine for infants aged 6 to 32 weeks was approved in February 2006 by the U.S. Food and Drug Administration. Otherwise, infection can be avoided by:

• Washing hands thoroughly with soap and water for 20 seconds after using the bathroom or changing diapers
• Washing hands thoroughly with soap and water for 20 seconds before eating
• Disinfecting contaminated surfaces such as counter tops and baby changing stations
• Not eating or drinking foods or liquids that might be contaminated

Chances of Developing Viral Gastroenteritis

Estimated global distribution of the 800,000 annual deaths caused by rotavirus diarrhea. Source: CDC^[1]

Gastroenteritis occurs all over the world, affecting people of every age, race and background. In developing nations, it's a leading cause of death in children.

Children in child care centers and older adults living in nursing homes are especially vulnerable.

Intestinal infections can flourish anywhere people congregate—from schools and dormitories to campgrounds and luxury cruise ships. Adults whose resistance is low—often because their immune systems are compromised by HIV, AIDS or other medical conditions—are especially at risk.

Each gastrointestinal virus has a season when it's most active. In the Northern Hemisphere, infections due to rotavirus or the Norwalk virus are most common between October and April.

Average time of peak rotavirus activity in the contiguous 48 states, July 1991 to June 1997. This contour plot was derived using the median value for time of peak activity for each laboratory. + indicates location of laboratories participating. Source: CDC^[1]

How Viral Gastroenteritis is Spread

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 two 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 there is suspicion about exposure to a virus in one of these settings or by foods prepared on the premise of places such as a restaurant, deli, or bakery, the local health department, which tracks outbreaks, can be contacted.

Research

The National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), through its Division of Digestive Diseases, supports basic and clinical research into gastrointestinal diseases, including epithelial cell injury in the gastrointestinal tract. New vaccines under development may decrease the risk of infection, especially among infants and young children.

References

1. ↑ ^{1.0 1.1 1.2} UD Parashar, JS Bresee, JR Gentsch, and RI Glass. Rotavirus. Emerging Infectious Diseases. Volume 4 No. 4/October-December 1998
2. ↑ US Food and Drug Administration, Bad Bug Book: Other Gastroenteritis Viruses.

External Links

American Dietetic Association

Center for Food Safety and Applied Nutrition

Gateway to Government Food Safety Information

Partnership for Food Safety Education: Fight BAC!(TM) education campaign

USDA: Food Safety Fact Sheets

CDC:

• Surveillance for Foodborne Disease Outbreaks
• PulseNet - The National Molecular Subtyping Network for Foodborne Disease Surveillance

NDDIC: Bacteria and Foodborne Illness

World Health Organization: Food Safety and Foodborne Illness