Epidemic

In epidemiology, 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"). (An epizootic is the same thing but for an animal population.) The disease may or may not be contagious.

Classification
Defining an epidemic can be subjective, depending in part on what is "expected". 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 like rabies may be classified as an "epidemic," while many cases of a common disease (like the common cold) would not.

Endemic diseases
Common diseases that occur at a constant but relatively high rate in the population are said to be "endemic." An example of an endemic disease is malaria in some parts of Africa (for example, Liberia) in which a large portion of the population is expected to get malaria at some point in their lifetimes.

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, mental illness or drug addiction. It can also be used metaphorically to relate a type of problem like those mentioned above.

Notable epidemics through history
Famous examples of epidemics include the bubonic plague epidemic of Medieval Europe known as the Black Death, and the Great Influenza Pandemic which coincided with the end of World War I.

Factors stimulating new epidemics
Factors that have been described by Mark Woolhouse and Sonya Gowtage-Sequeria to stimulate the rise of new epidemics include:
 * 1) Alterations in agricultural practices and land use
 * 2) Changes in society and human demographics
 * 3) Poor population health (e.g. malnutrition, 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 and the report by professor Akilesh Mishra .These include :
 * 1) Reduced levels of biodiversity (e.g. through environmental destruction)
 * 2) Bad urban planning

Pre-emptive measures
To protect us against the emergence of new epidemics, several preemptive measures have been proposed by professor Nina Marano, and Andy Dobson. These include:
 * To eat less food containing animal protein (eg meat, milk, milk-derivates)
 * To eat local food
 * To eat crops according to the season
 * To make agriculture more efficient
 * To avoid destruction of the rainforest
 * To be prepared to pay a higher price for meat

In addition, certain other measures are known to reduce the beneficial factors found above. As such, the measures would also decrease the possible emergence of new epidemics. These measures are:
 * Population control measures
 * Improving the urban planning

Renewed concern
In August 2007, the World Health Organization reported an unprecedented rate of propagation of infectious diseases.