Stomach Bug (Tummy Flu) – Causes, Incubation Period, Duration

What is Gastroenteritis, Stomach Flu, Tummy Bug?

Gastroenteritis is the inflammation of the stomach, small and large intestines and the term ‘stomach bug‘ is commonly used to describe a case of infective gastroenteritis. In these cases, the gastroenteritis is due to an infection by bacteria, virus or protozoa.

Another term commonly used for gastroenteritis is stomach or tummy flu which refers to viral gastroenteritis. This often occurs in seasonal episodes and can affect a number of people in the same environment (air borne) but it is not due to the infection with the influenza virus.

Food poisoning and traveler’s diarrhea also cause gastroenteritis either by the direct action of the microbe (bacteria, virus or protozoa found in food and water) on the stomach and bowels or by releasing toxins.

Causes, Incubation Period and Duration of Gastroenteritis


Incubation period less than 6 hours and duration of 1 to 2 days due to action of toxinw :

  • Bacillus cereus
  • Clostridium spp. (C.perfringens)
  • Staphylococcus aureus

Incubation period 12 to 72 hours and duration less than 8 days :

  • Campylobacter spp
  • Clostridium difficile (variable duration)
  • Escherichia coli – different serotypes
    • Enterotoxigenic E.coli (ETEC) causes gastroenteritis due to the action of  the enterotoxin.
    • Enterohemorrhagic E.coli (EHEC/Shiga toxin-producing E.coli) causes gastroeneteritis due to the action of verotoxins plus directly invade the mucosa of the small intestine and colon.
    • Enteroinvasive E.coli (EIEC) invades and destroys the colonic mucosal cells.
  • Salmonella spp
  • Shigella spp
  • Vibrio cholerae


Incubation period of 18 to 48 hours and duration less than 1 week :

  • Rotavirus
  • Norovirus

These are the most common but astroviruses, adenoviruses and sapoviruses may also cause viral gastroenteritis. Acute viral hepatitis should also be considered in a case of nausea and vomiting with other flu-like symptoms.


Incubation period of 1 to 4 weeks :

  • Amebiasis (UK ~ Amoebiasis) – duration 1 to 4 weeks
  • Cryptosporidiosis – duration 5 days to 4 weeks
  • Giardiasis – duration 3 to 10 weeks
  • Isosporiasis – duration is variable
  • Microsporidiosis – duration is variable

Isosporiasis and microsporidiosis is more frequently seen in cases of HIV/AIDS and duration depends on the patient’s immune status, accessibility to HAART and management. Persistent (>14 days) or chronic diarrhea (> 30 days), especially in adults, due to cryptosporidiosis should also raise the concern about HIV/AIDS.

Related Articles

  1. Stomach Flu (Tummy Bug) – Signs, Symptoms and Treatment
  2. Oral Rehydration and BRAT Diet (Diarrhea, Vomiting)
  3. HIV Diarrhea Symptoms – Causes of Watery, Bloody Stool in AIDS
  4. Food Poisoning – Causes, Symptoms, Diagnosis, Treatment
  5. What is the Incubation Period? List of Infections

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