A (from Greek παν ''pan'' all + δήμος ''demos'' people) is an Epidemic (an outbreak of an Infectious Disease ) that spreads through human populations across a large region (for example a continent), or even worldwide.
According to the World Health Organization (WHO), 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 merely because it is widespread or kills many people; it must also be infectious. For example Cancer is responsible for many deaths but is not considered a pandemic because the disease is not infectious or contagious (although certain causes of some types of cancer might be).
The ''WHO global influenza preparedness plan'' defines the stages of pandemic influenza, outlines the role of WHO and makes recommendations for national measures before and during a pandemic. The phases are:
Interpandemic period:
- Phase 1: No new influenza virus subtypes have been detected in humans.
- Phase 2: No new influenza virus subtypes have been detected in humans, but an animal variant threatens human disease.
Pandemic alert period:
- Phase 3: Human infection(s) with a new subtype but no human-to-human spread.
- Phase 4: Small cluster(s) with limited localized human-to-human transmission
- Phase 5: Larger cluster(s) but human-to-human spread still localized.
Pandemic period:
- Phase 6: Pandemic: increased and sustained transmission in general population.
There have been a number of significant pandemics recorded 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 Epidemic s that deserve mention above the "mere" destruction of cities:
- Peloponnesian War , 430 BC . Typhoid Fever killed a quarter of the Athenian troops and a quarter of the population over four years. This disease fatally weakened the dominance of Athens , but the sheer virulence of the disease prevented its wider spread; i.e. it killed off its hosts at a rate faster than they could spread it. The exact cause of the plague was unknown for many years; in January 2006 , researchers from the University Of Athens analyzed Teeth recovered from a Mass Grave underneath the city, and confirmed the presence of Bacteria responsible for typhoid. {Link without Title}
- Antonine Plague , 165 – 180 . Possibly Smallpox brought back from the Near East; killed a quarter of those infected and up to five million in all. At the height of a second outbreak (251–266) 5,000 people a day were said to be dying in Rome .
- The Black Death , started 1300s . Eight hundred years after the last outbreak, the Bubonic Plague returned to Europe . Starting in Asia , the disease reached Mediterranean and western Europe in 1348 (possibly from Italian merchants fleeing fighting in the Crimea ), and killed twenty million Europeans in six years, a quarter of the total population and up to a half in the worst-affected urban areas.
- Cholera
- ---first pandemic 1816 – 1826 . Previously restricted to the India n subcontinent, the pandemic began in Bengal , then spread across India by 1820. It extended as far as China and the Caspian Sea before receding.
- ---The second pandemic (1829–1851) reached Europe , London in 1832, Ontario Canada and New York in the same year, and the Pacific coast of North America by 1834.
- ---The third pandemic (1852–1860) mainly affected Russia , with over a million deaths.
- ---The fourth pandemic (1863–1875) spread mostly in Europe and Africa .
- ---In 1866 there was an outbreak in North America.
- ---In 1892 cholera contaminated the water supply of Hamburg, Germany , and caused 8,606 deaths.John M. Barry, (2004). ''The Great Influenza: The Epic Story of the Greatest Plague in History''. Viking Penguin. ISBN 0-670-89473-7.
- ---The seventh pandemic (1899–1923) had little effect in Europe because of advances in Public Health , but Russia was badly affected again.
- ---The eighth pandemic began in Indonesia in 1961, called El Tor after the strain, and reached Bangladesh in 1963, India in 1964, and the USSR in 1966.
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