Gastroenteritis
(Norwalk Virus · Stomach Flu · Norovirus)
In this condition factsheet:
The Facts on Gastroenteritis
Gastroenteritis literally means inflammation of the gastrointestinal tract. Viral gastroenteritis is also called "stomach flu." It is extremely common, especially in children, and is highly contagious. Bacterial gastroenteritis is also known as "food poisoning" and is caused by food that has been prepared or stored improperly. Gastroenteritis can also be caused by ingestion of drugs or chemical toxins (e.g. metals, plant substances).
Causes of Gastroenteritis
Viruses such as the norovirus (formerly known as Norwalk virus) cause gastroenteritis. Besides the norovirus, three other viruses are also common causes of gastroenteritis in North America: the rotavirus, the astrovirus, and the adenovirus, which tend to cause disease in infants and young children. They are spread by contaminated feces. From the feces, viruses find their way into food or water, or onto insects or people who later touch and contaminate food (fecal-oral transmission). Unfortunately, these viruses are tough enough to beat modern sanitation practices.
Norovirus is the typical form of gastroenteritis in adults and older children. It can occur at any time of year, but mostly occurs between November and April. This virus is spread by the fecal-oral route, and it may also be transmitted from person to person.
Rotavirus mostly affects unvaccinated infants aged 3 months to 3 years old. Before the introduction of vaccines, almost all children had been infected by the age of 5 years. It follows a seasonal occurrence, peaking in the late winter and early spring.
Adenovirus is another common cause of gastroenteritis in children under 2 years of age. It occurs at any time of year, with a slight increase in summer.
For infants, diapers are a major source of infection. Germs from the feces can get on both the baby's and the parent's hands.
Viruses cause disease by infecting or irritating cells within the wall of the small intestine. This causes fluids, minerals, and salts to flush into the intestines, leaving the body as diarrhea.
Food poisoning results when a person eats food that has grown bacteria that can cause gastroenteritis. The symptoms of food poisoning are caused either by the bacteria themselves or by the byproducts (toxins) they produce. Symptoms of food poisoning can begin within a few hours or a few days after eating the contaminated food, depending on whether the bacteria or the toxin causes the problem.
Symptoms and Complications of Gastroenteritis
Some people who become infected with these viruses won't have any symptoms. The actual rate of infection with these viruses is far higher than the rate of gastroenteritis. Once in a while, an adult will get an infection severe enough to be noticeable. Young children are much more likely to feel symptoms.
Norovirus, when symptomatic, causes the classic "24-hour" gastroenteritis that strikes adults. Symptoms include vomiting and diarrhea. Bowel movements are usually loose and watery, but there is typically no mucus or blood. Low fever, abdominal cramps, aching muscles, and headache are also possible. Both rotavirus and norovirus tend to produce the first symptoms 1 to 3 days after infection. Most people recuperate within 2 or 3 days without any serious or long-lasting health effects.
Young children with rotavirus may have severe watery diarrhea lasting about a week, which can lead to dehydration. Rotavirus also causes vomiting and a significant increase in temperature.
Adenovirus can produce up to 2 weeks of diarrhea for young children, with occasional mild vomiting and sometimes a low fever. It may take over a week before symptoms appear.
Astrovirus creates symptoms similar to a mild rotavirus infection.
Symptoms of food poisoning often include nausea, general weakness or exhaustion, headache, abdominal pain and cramps with abrupt vomiting, and diarrhea. If symptoms last more than 48 hours, your doctor may want to obtain a blood and stool sample as well as to test the food in question.
A young child with fever and diarrhea or vomiting should be seen by a doctor. It is not essential for adults to seek medical advice unless vomiting and diarrhea are severe or medical conditions coexist, as the symptoms usually go away on their own. However, if vomiting or severe diarrhea persist for more than 1 week, call your doctor.
You should also contact your doctor if the following symptoms are present:
- blood in vomit or stool
- a hard, swollen, painful abdomen
- high fever
- chills
- excessive thirst, dry mouth
- excessive lethargy
- dizziness or lightheadedness when changing position (e.g., moving from sitting to standing)
