Tuesday, November 30, 2010

The Stomach Flu

Let's just get it out of the way right here at the beginning. There is no such thing as the stomach flu. The flu (short for influenza [1]) is caused by a virus which infects the respiratory tract. The most common symptoms of the disease are catarrh [2], chills, coughing, fatigue, fever, headache, malaise [3], muscle aches, and a sore throat.[4] Only very rarely is the flu accompanied by vomiting and never by diarrhea. So if what you have isn't called the stomach flu, then what should it be called? Gastroenteritis.

Gastroenteritis is caused by a variety of pathogens, but most often the culprit is a virus. There are, however, bacteria, fungi, toxins, and parasites that can also cause gastroenteritis.[5] The most common gastroenteritis-causing virus is norovirus. Norovirus causes over 50% of gastroenteritis cases, including cases of food poisoning. It is the most common disease that breaks out during cruise ships.[6] Another ~20% of cases of gastroenteritis are caused by rotavirus, which usually infects children but rarely adults.[7] Less significant causes of gastroenteritis are adenoviruses and astrovirus. All are spread through the oral-fecal route (which is why you should always wash your hands after you go to the bathroom and before you prepare food). Since young children are unaware of personal hygiene and touch themselves a lot, they are more susceptible to gastroenteritis than adults.

So now that you know that the proper name is gastroenteritis, let's never hear anyone say "stomach flu" again. Deal?


[1] The name influenza is borrowed from the Italian word influenza (itself from the Latin influentia), which means "influence". This refers to the astrological influence that the stars had on earthly events. Whenever a plague or epidemic happened (which is how the word was originally used), early Europeans believed that the stars were involved. In 1743 there was an epidemic of the grippe (the French name for the flu) but rather than call it influenza di catarro (the grippe epidemic), English speakers just called it influenza. See http://en.wikipedia.org/wiki/Influenza#Etymology and OED, Second Edition (1989), influenza n def. a.

[2] Catarrh is swelling of the mucous membranes. This can result in
  • a stuffy nose
  • stuffy sinuses
  • swollen tonsils
  • swollen adenoids
  • coughing and/or sneezing up phlegm.
[3] Malaise is that icky feeling you get when you're sick.

[5] See http://en.wikipedia.org/wiki/Gastroenteritis. An adverse reaction to food or medication can also result in gastroenteritis.

[7] In fact most children have been infected with rotavirus at least once by the time they reach the age of 5. See http://en.wikipedia.org/wiki/Rotavirus.

Image attribution:

False-color electron micrograph of norovirus is in the public domain (produced by Charles D. Humphrey at the CDC), available at http://phil.cdc.gov/phil/home.asp (search for "norovirus").

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