Bacterial infection in stomach and intestines is mainly caused due to consumption of contaminated food or water. At times, the way the food items are handled or stored at grocery stores or the way in which these foods are prepared at the food joints, may be responsible for contamination of food items. Campylobacter jejuni, Clostridium, Shigella, Salmonella, Escherichia coli or Staphylococcus aureus figure in the list of common bacteria that may cause stomach flu.

The symptoms usually appear soon after the ingestion of contaminated water or foods. As the bacteria grow in numbers, they may also react with the food present inside the gastrointestinal tract, and start producing toxins. This leads to the inflammation of the gastrointestinal tract. Since some of the bacteria may be found in poultry, it is essential that you wash your hands after handling animals that may be infected. Those who don't do so, are at an increased risk of developing gastroenteritis. Sometimes bacteria may be present in human feces, and if the infected person doesn't wash his hands properly after defecating, the surfaces or objects he/she touches may become contaminated. It is therefore, essential that one pays attention to hygiene.