Stomach flu is caused by different types of stomach viruses. Stomach flu should not be confused with the flu or influenza. This name is misleading as the stomach flu does not affect the stomach but is actually a viral infection of the intestines.
There are many different types of stomach viruses which can enter the gastrointestinal tract and settle in the stomach or the intestine. These viruses incubate in these organs and multiply and thus cause the infection known as stomach flu, gastric flu or gastroenteritis.
Some of the common types of stomach virus which can cause stomach flu are as follows:
- Rotavirus: this is the main cause of stomach flu in toddlers and infants and sometimes even older children. It can also infect adults who are in close contact with the infected children. It takes a day or two after exposure for the symptoms of rotavirus to appear. The child may have watery diarrhea along with vomiting, nausea, abdominal pain and fever. These symptoms last from about three days to a week. The incubation period of this virus is about forty eight hours. This stomach virus is extremely contagious.
- Adenovirus: this stomach virus has about forty nine variants of which just one or two strains affect the gastrointestinal tract. It occurs mainly in children under the age of two years. The symptoms of this stomach virus are vomiting and diarrhea and these appear about a week after exposure. The incubation period of this virus is about a week.
- Caliciviruses: this family of stomach viruses can cause stomach flu in people of all ages. They are supposed to be the main cause of stomach flu in adults. There are four types of calicivirus of which the norovirus is the most common. The symptoms of this virus are vomiting, diarrhea, headache and fatigue. These symptoms appear within one to two days of exposure. The Norwalk virus is a type of norovirus. The incubation period of this virus is twelve to forty eight hours. These stomach viruses can withstand freezing but can be killed with boiling.
- Astrovirus: Children, infants and the elderly are normally infected by this stomach virus. The symptoms of vomiting and diarrhea usually appear within one to three days of exposure. It is most active during the winter months. The incubation period of this virus is one to five days. There are seven types of the astrovirus.
Stomach flu can be quite contagious and the viruses are transmitted usually through people with unwashed hands. People can also catch the virus when they are in close contact with other infected people. Sharing food, water and eating utensils with those who have the stomach flu can transmit the infection. Contaminated food and water can also spread the virus to others. A person can be contagious even after the symptoms of stomach flu have cleared. The stomach virus can be found in their stool for nearly two weeks after recovery from the illness.
There can be outbreaks of stomach flu in child care centers, cruise ships, dormitories, camps, restaurants, schools and even in households. The stomach virus can be picked up in places where groups of people gather.
Stomach flu can lead to dehydration which is the main symptom of the stomach virus which should be treated. Dehydration can occur due to the loss of body fluids caused by diarrhea and vomiting. Solid food should be stopped completely as the patient will not be able to retain it. Instead fluids should be given in small doses.
All the different types of stomach viruses attack the cells lining the small intestine and that is why the symptoms of stomach flu with any of these viruses are similar.