Intestinal viruses cause a condition called viral gastroenteritis. According to the National Digestive Diseases Information Clearinghouse, viral gastroenteritis is the second most common illness in the United States, causing millions of cases of diarrhea each year. It is highly contagious and, while usually mild, can cause severe disease in the elderly, in very young children and in those with a weakened immune system.
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There are several viruses that cause gastroenteritis. Rotavirus is the most common cause of gastroenteritis in children. It usually affects children less than 2 years old, mostly during the winter and spring. Caliciviruses cause disease in all age groups. One of them, the norovirus, is responsible for epidemics of gastroenteritis between the months of October and April. And even though viral gastroenteritis is called "the stomach flu," the flu virus usually does not cause gastroenteritis,
The main symptoms of an intestinal virus are diarrhea, nausea and vomiting. The stools become watery and foul smelling. According to the Merck Manuals, the stool can contain specks of blood or mucus. The nausea can be sudden and can lead to loss of appetite and frequent bouts of emesis, or vomiting. Vomiting is usually nonbilious, meaning it does not contain yellowish bile, a substance present in the intestines to help digest foods. But if the vomiting becomes severe, it can contain bile or even specks of blood. Vomiting makes it hard for the person to stay hydrated.
Dehydration follows persistent vomiting and diarrhea. According to the Merck Manuals, the symptoms of dehydration include weakness, decreased urination, dry mouth and lips, and rapid heart rate, as the heart tries to compensate for the decrease in fluids by pumping more blood around the body. Persistent vomiting and diarrhea from gastroenteritis can lead to severe electrolyte imbalances. Specifically, the levels of two important electrolytes, potassium and sodium, can decease. This can lead to cardiac rhythm abnormalities, kidney failure and, in severe cases, shock.
The diarrhea and vomiting can lead to abdominal pain. The pain is usually crampy, diffuse and accompanied by a feeling of bloating. As the vomiting continues, the pain can get worse. Also, certain microorganisms can produce a lot of gas within the intestines, causing bowel distension and further pain. The intestines can also become hyperactive, which can cause audible rumbling noises within the abdomen.
The treatment for an intestinal virus is providing supportive care while the body gets rid of the infection. This includes hydration, either by mouth or via intravenous fluids; anti-emetics to decrease the nausea and vomiting; and correction of electrolyte abnormalities. People with severe dehydration due to gastroenteritis may need close monitoring in an intensive care unit, especially if they have signs of kidney failure or shock.