People often wonder, what causes stomach flu or gastroenteritis. The infection can be caused by different types of viruses and bacteria. Parasites, toxins, food allergies and to a certain extent some medication can also cause stomach flu. Sometimes the symptoms of stomach flu worsen and the condition progresses to another disease.

The main cause for stomach flu is viral. There are several viruses that can cause this ailment and each of these has various strains. Some of the most common viruses which cause stomach flu are listed below.

  • Rotavirus: this is a virus which causes diarrhea and vomiting in young children and in infants. It has an incubation period of about forty eight hours and children are generally more sick with this virus than with others. This virus is extremely contagious and it is shed through the feces, nasal secretions and through the vomit. The virus lasts for a few weeks after the symptoms disappear. There is danger of dehydration when the child is infected with rotavirus.
  • Calicivirus: this is a family of a variety of viruses. Norwalk virus, Norovirus and Sapovirus are all part of the Calicivirus family. These are the main cause of stomach flu or gastroenteritis in adults and also in children. In the US alone, Norovirus accounts for about 50% to 70% of the cases of stomach flu in adults. The incubation period of this virus is between twelve to forty eight hours. If this virus is present in food it can be killed by boiling. People who have this virus are contagious for at least three days after the symptoms of stomach flu stop.
  • Astrovirus: this virus affects children and in a milder way, even adults. It has an incubation period of at least one to five days. There are about seven types of this particular virus.
  • Adenovirus: stomach flu can be caused in adults and children with this virus. There are many strains of this virus and only two are known to cause gastroenteritis. It has an incubation period of about a week.


Sometimes the cause for stomach flu can be bacterial. Some of these are as follows:

  • E-coli: this bacteria causes food poisoning and other infections.
  • Staphylococcus: this is responsible for stomach cramps and diarrhea.
  • Salmonella: responsible for food poisoning and causes diarrhea and vomiting.
  • Listeria: this is found in contaminated dairy products.
  • Shigella: causes dysentery
  • Campylobacter: this is also found in contaminated dairy food.

These are a few bacteria which cause stomach flu and other related diseases. To prevent bacterial gastroenteritis care must be taken to handle, cook and store food and drinking water hygienically. Stomach flu can be prevented by maintaining hygiene.


Parasites like Giardia, Cryptosporidium and Entamoeba are found in contaminated water and are a common cause of diarrhea. Drinking water should be boiled and filtered and stored in sterile containers.

Sometimes stomach flu can be caused by food allergies. Some of the common allergies could be to eggs, shellfish, milk and nuts. These can cause some of the symptoms of stomach flu.

Toxins found in shellfish and other sources could be the cause of stomach flu. Some medication can cause an upset stomach as a side effect.

The symptoms of stomach flu can range from mild to severe depending on the cause. Treatment for a mild attack can be done through simple home remedies such as a complete fluid diet for a few days and then slowly change to a bland semi-solid diet and eventually to a normal diet which is non spicy and without any fat content. If the symptoms of stomach flu worsen then laboratory tests need to be conducted to determine the cause of the stomach flu and appropriate treatment can be given.

The causes of stomach flu are varied and the infection can be prevented by maintaining a high level of hygiene.


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