What is a Pandemic?
A pandemic, or global epidemic, is an outbreak of an infectious disease that affects people over an extensive geographical area (from Greek pan all + demos people).
Common killers and pandemics
According to the World Health Organization, a pandemic can start when three conditions have been met:
the emergence of a disease new to the population
the agent infects humans, causing serious illness
the agent spreads easily and sustainably among humans.
A disease or condition is not a pandemic specifically because it kills a large number of people. For example, the class of diseases known as cancer is responsible for a large number of deaths. But the deaths and disabilities due to cancer are not considered a pandemic because the condition is not infectious (although certain infectious agents are known to increase cancer risk).
Pandemics through history
There have been a number of significant pandemics in human history, generally zoonoses that came about with domestication of animals - such as influenza and tuberculosis. There have been a number of particularly significant epidemics that deserve mention above the 'mere' destruction of cities.
Concerns about possible future pandemics
Diseases that may possibly attain pandemic proportions include Lassa fever, Rift Valley fever, Marburg virus, Ebola virus and Bolivian hemorrhagic fever. As of 2004, however, emergences of these diseases into the human population in recent years has shown their virulence is so high they have burned out in geographically confined areas. Thus their effect on humans is currently limited.
HIV - the virus that causes AIDS - can be considered a global pandemic but it is currently most extensive in southern and eastern Africa. It is restricted to a small proportion of the population in other countries, and is only spreading slowly in those countries. If there were to be a true destruction-of-life pandemic it would be likely to be similar to HIV, i.e. a constantly evolving disease.
Antibiotic-resistant superbugs may also revive diseases previously regarded as 'conquered'.
In 2003, there were concerns that SARS, a new highly contagious form of pneumonia, might become pandemic.
There is also a historical record of Influenza pandemics of varying severity at 20-40 year intervals. In February 2004, avian influenza virus was detected in pigs in Vietnam, increasing fears of the emergence of new variant strains. It is feared that if the avian influenza virus combines with a human influenza virus (in a pig or a
human), the new subtype created could be both highly contagious and highly lethal in humans. Such a subtype could cause a global influenza pandemic, similar to the Spanish Flu, or the lower mortality pandemics the Asian Flu and the Hong Kong Flu.
In November 2004 the director for the western region of the World Health Organization said that an influenza pandemic was inevitable and called for urgent plans to combat the virus.
In May 2005, scientists urgently call nations to prepare for a global influenza pandemic that could strike as much as 20% of the world's population.
In October 2005, cases of the Avian flu (the deadly strain H5N1) were identified in Turkey. EU Health Commissioner Markos Kyprianou said: "We have received now confirmation that the virus found in Turkey is an avian flu H5N1 virus. There is a direct relationship with viruses found in Russia, Mongolia and China." Cases of bird flu were also identified shortly thereafter in bordering Romania, and then Greece.
Possible cases of the virus have also been found in Croatia, Bulgaria and in the United Kingdom. However, by the end of October only 67 people had died as a result of H5N1 which was atypical of previous influenza pandemics.
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