Stomach flu, officially called viral gastroenteritis, is caused by several viruses, according to the website eMedTV.com. The symptoms of stomach flu are usually the same regardless of the virus, but some symptoms can be more severe than others. Stomach flu viruses damage the cells in the lining of the small intestine, allowing fluids to leak into the intestine, which causes diarrhea, according to eMedTv.com. Several viruses cause the stomach flu, but the four main virus types are rotavirus, adenovirus, caliciviruses and astrovirus.
Rotavirus
As suggested by eMedTV.com, rotavirus is the most common cause of stomach flu in children between 3 months and 15 months of age. Symptoms can occur within one to two days of contracting the virus. Typical symptoms are vomiting, watery diarrhea, fever and abdominal pain lasting between three and eight days. The Centers for Disease Control and Prevention (CDC) says the rotavirus can lead to severe diarrhea, hospitalization and even death.
Adenovirus
Forty-nine types of adenoviruses exist and only one type affects the gastrointestinal tract, causing vomiting and diarrhea, according to eMedTV.com. Typically this virus affects children under the age of 2 years.
Caliciviruses
Caliciviruses infect children and adults. The most common of the caliciviruses is the norovirus, which causes stomach flu symptoms such as vomiting, diarrhea, fatigue, headache and even muscle aches, according to eMedTV.com. Caliciviruses are thought to be the cause of at least 50 percent of gastroenteritis attributed to food. Food can become contaminated by viruses when an infected person shares utensils, food or drink with others, according to the CDC. Most stomach flu viruses are highly contagious and can be spread through inadequate hygiene, including infrequent hand-washing.
Astrovirus
Astrovirus is most likely to infect children, infants and the elderly, according to eMedTV.com. Stomach flu from this virus is most likely to occur in the winter months with symptoms appearing within one to three days of contraction.
