Epidemic vs Pandemic

"Epidemic" and "pandemic" are both used to describe widespread outbreaks of a disease but there are some subtle differences between the two words.

Comparison chart

Improve this chart	Epidemic	Pandemic
Definition:	An epidemic occurs when the incidence rate (i.e. new cases in a given human population, during a given period) of a certain disease substantially exceeds what is "expected," based on recent experience.	A pandemic is an epidemic of an infectious disease that spreads through human populations across a large region, like a continent.

1 Definitions
2 Differences between an epidemic and a pandemic
3 Video explaining the differences
4 See Also

edit Definitions

An epidemic (from Greek epi- upon + demos people) is a classification of a disease that appears as new cases in a given human population, during a given period, at a rate that substantially exceeds what is "expected," based on recent experience (the number of new cases in the population during a specified period of time is called the "incidence rate").

A pandemic (from Greek pa? pan all + d?µ?? demos people) is an epidemic that spreads across a large region (for example a continent), or even worldwide.

edit Differences between an epidemic and a pandemic

Simply put, when an epidemic gets out of hand, it is called a pandemic. This has 2 nuances:

Geographical spread
- An epidemic that is not localized to a city or a small region but spans a larger geographical area can be called a pandemic.
Incidence rate
- An epidemic may be localized to a small region but the number of people affected may be very, very large compared to what is "expected". In this case, it can be called a pandemic even if its geographical spread is not very large. For example, let us say that a disease has an "expected" rate of infection of 15%. When 40% of the population of a state is infected, we have an epidemic on our hands. When 75% of the population is infected, it has reached pandemic proportions.

edit Video explaining the differences

In this video, Dr. Kenneth Alexander, chief of pediatric infectious diseases at the University of Chicago Medical Center, explains the differences between an outbreak, an epidemic and a pandemic and others questions about the swine flu outbreak.

edit See Also

Comments: Epidemic vs Pandemic

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Anonymous comments

The Spanish Flu pandemic (1918-20) did indeed have a worldwide distribution. Pandemics are often given names based on the region/country of origin, or the place of the original epidemic before they become pandemic. Naming allows epidemiologists to communicate the original organism/strain from others which may cause similar diseases.
94.✗.✗.114 on 2013-04-13 14:54:29

hmmmm....."word shift", as you put it, does sometimes occur but not in all cases you've mentioned. Tsunami has always been the correct term in that "tidal" has been somewhat of a misnomer since tsunamis have nothing to do with tides. Pandemic has always been a valid term since it describes the severity of epidemic. All pandemics are epidemics but not all epidemics are pandemics.
128.✗.✗.7 on 2012-03-22 17:13:52

This is a prime example of what I refer to as a wordshift. This happens frequently in our trendy and restless contemporary society. There is really very little actual difference in the conditions the two words describe. It is merely change solely for the sake of change. "X" has always been called such and such and that's just plain boring so let's find a new word for it. Thus a swamp is now a 'wetland'; a jungle is now a 'rain forest'; a tidal wave a 'trunami'; a liberal is now a 'progressive'; and yes, a pain old epidemic is now a 'pandemic'. But someone try to find a 'pandemiologist'.
98.✗.✗.91 on 2011-03-12 13:22:32

America's Forgotten Pandemic: The Influenza of 1918, o Author: Alfred Crosby o Publisher: Cambridge: Cambridge University Press, 1989 o ISBN: 0521833949
174.✗.✗.70 on 2009-11-29 14:43:02

The main point here is this......."Epidemic" became "Pandemic" when the Spanish Flu finally encompassed the worldwide human race and circled the globe with infection and death.
96.✗.✗.64 on 2009-11-29 05:40:40

Pandemic or Pandemonia Pandemic?
119.✗.✗.212 on 2009-04-30 03:42:06

Go back and read the definition. It says, "Simply put, when an epidemic gets out of hand, it is called a pandemic." Is it possible that no one is really trying to scare you but merely reassess the data using that (above) definition?
75.✗.✗.35 on 2009-04-28 03:07:28

I agree, we as people are always giving our attentions to scare mongers, i.e. govenerment. Always trying to scare us into giving them more control. Becareful what words you use to whip up fear.
70.✗.✗.184 on 2009-04-27 21:42:43

I defy anyone to find a reference to the Spanish Flu Epidemic of 1919 as a Pandemic, before the mid-1990's. Research it. It was always called Epidemic before 1995, Pandemic afterwards. Look at the references too. Those before 1995 always used the word "epidemic" and no other word. I don't think the epidemic of 1919 got worse after 1995. Word inflation did. What I'm expecting the verbal inflaters to do is go back and try to wipe out or change the old references to epidemic. That word is simply not scary enough. Pandemic is, at least for now.
206.✗.✗.31 on 2009-04-24 21:48:07