A pandemic, or global epidemic, is an outbreak of an infectious disease that
affects people or animals over an extensive geographical area (from Greek pan
all + demos people).
Common killers and pandemics
A disease or condition is not pandemic specifically because it kills a lot 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, all of them
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:
Peloponnesian War, 430 BCE. An unknown agent 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.
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.
Plague of Justinian, started 541. The first recorded outbreak of the bubonic
plague. It started in Egypt and reached Constantinople the following spring,
killing (according to the Byzantine chronicler Procopius) 10,000 a day at its
height and perhaps 40 percent of the city's inhabitants. It went on to destroy
up to a quarter of the human population of the eastern Mediterranean.
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 Indian 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.
The sixth pandemic (1899-1923) had little effect in Europe because of advances
in public health, but Russia was badly affected again.
The seventh 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.
The "Spanish Flu", 1918-1919. Began in August 1918 in three disparate locations:
Brest, Boston and Freetown. An unusually severe and deadly strain of influenza
spread worldwide. The disease spread across the world, killing 25 million in the
course of six months; some estimates put the total of those killed worldwide at
over twice that number. An estimated 17 million died in India, 500,000 in the
USA and 200,000 in the UK. It vanished within 18 months and the actual strain
was never determined, though some recent attempts at reconstructing genes from
the virus have been successful.
The "Asian flu," 1957-58. A H2N2 caused about 70,000 deaths in the United
States. First identified in China in late February 1957, the Asian flu spread to
the United States by June 1957.
The "Hong Kong flu," 1968-69. A H3N2 caused about 34,000 deaths in the United
States. This virus was first detected in Hong Kong in early 1968 and spread to
the United States later that year. Influenza A (H3N2) viruses still circulate
today.
The epidemic disease of wartime was typhus, sometimes called "camp fever"
because of its pattern of flaring up in times of strife. (It is also known as "gaol
fever" and "ship fever", for its habits of spreading wildly in cramped quarters,
such as jails and ships.) Emerging during the Crusades, it had its first impact
in Europe in 1489 in Spain. During fighting between the Christian Spaniards and
the Muslims in Granada, the Spanish lost 3,000 to war casualties and 20,000 to
typhus. In 1528 the French lost 18,000 troops in Italy and lost supremacy in
Italy to the Spanish. In 1542, 30,000 people died of typhus while fighting the
Ottomans in the Balkans. The disease also played a major role in the destruction
of Napoleon's grande armée in Russia in 1811. Typhus also killed numerous
prisoners in the Nazi concentration camps during World War II.
Encounters between European explorers and populations in the rest of the world
often introduced local epidemics of extraordinary virulence. Disease killed the
entire native (Guanches) population of the Canary Islands in the 16th century.
Half the native population of Hispaniola in 1518 was killed by smallpox.
Smallpox also ravaged Mexico in the 1520s, killing 150,000 in Tenochtitlán
alone, including the emperor, and Peru in the 1530s, aiding the European
conquerors. Measles killed a further two million Mexican natives in the 1600s.
As late as 1848-49, as many as 40,000 out of 150,000 Hawaiians are estimated to
have died of measles, whooping cough and influenza.
There are also a number of unknown diseases that were extremely serious but have
now vanished, so the etiology of these diseases cannot be established. Examples
include the previously mentioned plague in 430 BCE Greece and the English Sweat
in 16th-century England, which struck people down in an instant and was more
greatly feared even than the bubonic plague.
Concern about possible future pandemics
Diseases that may possibly attain pandemic proportions include Lassa fever, Rift
Valley fever, Marburg virus, Ebola virus and Bolivian haemorrhagic fever. As of
2002, however, the recent emergence of these diseases into the human population
has shown their virulence is high, such that they tend to 'burn out' in
geographically confined areas or that 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 have 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 undergoes antigenic shift with a human
influenza virus, 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 flu
pandemic that could strike as many as 20% of the world's population.
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