What’s a "Stomach Bug" or "Stomach Flu?"

Many have their own special terms for stomach and intestinal related illness such as, “My daughter had the ‘stomach bug’ last week and now it is going through the whole house.” Or, “I had vomiting and diarrhea all night. What misery! I think I had the ‘stomach flu.’”

The “stomach bug” or “stomach flu” is actually gastroenteritis, which is not the same as the influenza virus. Influenza or “flu” usually does not cause symptoms such as vomiting or diarrhea. So, what is gastroenteritis and what causes this distress?

Gastroenteritis is an inflammation of the stomach and small and large intestines. Symptoms are diarrhea, nausea or vomiting, abdominal cramps, and often a fever. Gastroenteritis is caused by viruses, bacteria or parasites.


Viral — Individuals who have viral gastroenteritis have contracted the illness primarily through infected fecal matter. Two common types of viral gastroenteritis are norovirus and rotavirus.

  • Norovirus — These viruses are found in the vomit and stool of infected people. You can get it by: eating food or drinking liquids that are contaminated with norovirus, touching surfaces or objects contaminated with norovirus and then putting your hand or fingers in your mouth, or by having direct contact with a person who is infected with norovirus (for example, when caring for someone with norovirus or sharing foods or eating utensils with them).
    • People with norovirus illness are contagious from the moment they begin feeling sick until at least 3 days after they recover. But, some people may be contagious for even longer
    • When wide-spread infections occur on cruise ships or in school systems, norovirus is a common culprit.
  • Rotavirus — Rotavirus is contracted directly through infected fecal matter and occurs predominantly in winter and spring. In the US, contagious outbreaks are common in childcare centers, hospitals, and nursing homes.
    • Frequent hand washing is the best tool to limit the spread of rotavirus infection, as well as vaccination which is now offered in the routine line up of infant immunizations

Bacterial — When improperly handled food or water containing bacteria is consumed, this may result in bacterial gastroenteritis. Undercooked meats, unclean utensils, untreated water, raw foods, and unwashed hands can all cause different strains of bacteria in what we eat or drink. Two of the most commonly known bacteria that cause gastroenteritis are E.coli and Salmonella.

E.coli — Although E.coli bacteria normally live in intestines, certain strains can cause inflammation of the small intestine and mild to severe food poisoning. When dangerous forms of E.coli are present in food and beverage products and distributed through the supply chain, there are often product recalls to prevent further illness and even death in individuals who have consumed the products.

Salmonella — Salmonella bacteria causes an infection of the lining of the small intestine. Salmonella outbreaks are also caused by unclean food equipment and improperly prepared food, particularly undercooked poultry and eggs. Salmonella can also be contracted from certain reptile pets, such as turtles, lizards, and snakes, which can carry the bacteria.

Parasitic — Gastroenteritis can also be caused by parasites such as protozoa, nematodes, and amoeba. Which can be spread on dirty hands, on the soiled surfaces of toys or bathrooms or through contaminated drinking or swimming water.

  • Giardia is the most common cause of parasitic gastroenteritis in the United States.


  • Wash hands often and thoroughly.
  • Avoid potentially contaminated water and food.
  • Avoid contact with infected individuals when possible.
  • Cook food thoroughly. When in doubt, throw it out.
  • Clean kitchen surfaces and equipment thoroughly.
  • Do research before swimming. Has the water been tested?
  • When sick, stay home so others do not become infected.

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