Cause of Stomach Flu
The cause of stomach flu (viral gastroenteritis) is a virus that damages the cells lining the small intestine. Any one of many viruses may be the cause of stomach flu; viruses that commonly cause stomach flu include rotaviruses and noroviruses. Each virus results in similar symptoms, although some viruses tend to occur primarily in certain groups of people (such as infants and the elderly).
The cause of stomach flu (the medical term is viral gastroenteritis) is an infection with a stomach flu virus. Technically, the term "stomach flu" is not correct. This is because the so-called stomach flu is not caused by the influenza virus and it does not infect the stomach. Instead, each type of stomach flu virus causes stomach flu symptoms by damaging the cells in the lining of the small intestine. As a result, fluids leak from the cells into the intestine and produce watery diarrhea.
The cause of stomach flu is not bacteria (such as Salmonella or Escherichia coli), parasites (such as Giardia), medications, or other medical conditions, although the symptoms may be similar. Your doctor can determine if the diarrhea is caused by a virus or by something else.
Many different viruses can cause stomach flu. Some common types of stomach flu viruses include:
Rotavirus is the leading cause of stomach flu among children 3 months to 15 months old, and is the most common cause of diarrhea in children under the age of 5 years. Rotavirus symptoms 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. This type of stomach flu virus can also infect adults who are in close contact with infected children, but the symptoms in adults are milder (see Adult Rotavirus). In the United States, rotavirus infections are most common from November to April.