Skip to content
My WebMD Sign In, Sign Up

Cold, Flu, & Cough Health Center

Font Size

What Is a Pandemic?

Confused about what a pandemic is versus an epidemic? WebMD explains.
WebMD Feature

"Pandemic flu" has been one of the buzzwords of late 2005. But how does the phrase that's on everyone's lips differ from "epidemic," that other well-worn disease term?

Apparently, a lot of people aren't sure. Merriam-Webster reports that "pandemic" is the seventh most frequently looked-up word in its online dictionary this year. The definition: "occurring over a wide geographic area and affecting an exceptionally high proportion of the population."

Recommended Related to Cold & Flu

Swine Flu 101: College Survival Tips


Read the Swine Flu 101: College Survival Tips article > >

This is almost the same as the dictionary definition for "epidemic," and it doesn't explain much when it comes to influenza -- a.k.a. the flu.

An epidemic of influenza is different from the dreaded pandemic that scientists and world health officials fear is nigh. We might see an epidemic of seasonal influenza during any given year. In fact, we just had one.

Flu reached epidemic levels in the U.S. for 10 weeks in a row during the 2004-2005 season. Records kept by the CDC show that during the week ending March 5, 2005, 8.9% of all deaths reported in 122 U.S. cities were due to influenza and pneumonia (a common complication of the flu).

The CDC's definition of a flu epidemic relates to the percentage of deaths in a given week caused by influenza and pneumonia. The "epidemic threshold" is a certain percentage above what is considered normal for that period. The normal level, or baseline, is statistically determined based on data from past flu seasons.

Christine Pearson, a spokeswoman for the CDC, cautions that the definition of an influenza epidemic doesn't apply to other diseases.

Seasonal flu epidemics may sicken millions, but those who die are typically a small number of the elderly, very young children, and people with weak immune systems. That's not the case during the worst influenza pandemics.

There are two main features of an influenza pandemic. First, the virus is a new strain that has never infected people before. Second, it's on a global scale. Sometimes it's also unusually deadly.



The Next Pandemic

The world is closely watching a virus known as avian influenza H5N1, or "bird flu." Don't confuse it with pandemic flu. It isn't one. At least, it isn't one yet.

Today on WebMD

neti pot
Chicken soup
Natural Cold Flu Remedies Slideshow
Syringes and graph illustration
Natural Cold Flu Remedies Slideshow
blowing nose
Allergy And Sinus Symptom Evaluator
Health Check
Boy holding ear
woman receiving vaccine shot
Bacterial or Viral Infection
How To Calm Your Cough
Sore Throat

WebMD Special Sections