In epidemiology, an epidemic (epi- meaning "upon or above" and demic- meaning "people"), occurs when new cases of a certain disease, in a given human population, and during a given period, substantially exceed 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"). (An epizootic is the analogous circumstance within an animal population.) In recent usages, the disease is not required to be communicable; examples include cancer or heart disease. Another example includes the infamous Black Death of the Middle Ages.



Defining an epidemic can be subjective, depending in part on what is "expected" -- see also Endemic (epidemiology). An epidemic may be restricted to one locale (an outbreak), more general (an "epidemic") or even global (pandemic). Because it is based on what is "expected" or thought normal, a few cases of a very rare disease may be classified as an "epidemic," while many cases of a common disease (such as the common cold) would not.


The term syndemic refers to interacting epidemics that increase the health burden of affected populations. Social conditions that heighten the health risk of populations (e.g. poverty, discrimination and stigmatization, and marginalization) by increasing stress, malnutrition, interpersonal violence, and the experience of deprivation, increase the clustering of epidemic diseases and the likelihood of their interacting.

Non-infectious disease usage

The term "epidemic" is often used in a sense to refer to widespread and growing societal problems, for example, in discussions of obesity or drug addiction. It can also be used metaphorically to relate a type of problem like those mentioned above.

Factors stimulating new epidemics

Factors that have been described by Mark Woolhouse and Sonya Gowtage-Sequeria to stimulate the rise of new epidemics [1] include:

  1. Alterations in agricultural practices and land usage
  2. Changes in society and human demographics
  3. Poor population health (e.g., malnutrition, high prevalence of HIV)
  4. Hospitals and medical procedures
  5. Evolution of the pathogen (e.g., increased virulence, drug resistance)
  6. Contamination of water supplies and food sources
  7. International travel
  8. Failure of public health programs
  9. International trade
  10. Climate change

Several other factors have also been mentioned in different reports, such as the report by professor Andy Dobson [2] and the report by professor Akilesh Mishra [3].These include :

  1. Reduced levels of biodiversity (e.g. through environmental destruction)
  2. Bad urban planning

Pre-emptive measures

To protect the population against the emergence of new epidemics, several preemptive measures have been proposed by the World Health Organization [4].

Renewed concern

1. Mar. 2009 - The Influenza A, aka the "H1N1" virus, a subtype of influenza virus A and the most common cause of influenza in humans.

2. Aug. 2007 - the World Health Organization reported an unprecedented rate of propagation of infectious diseases.[5]

See also



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