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  • We live in an interconnected, an increasingly globalized world.

  • Thanks to international jet travel,

  • people and the diseases they carry

  • can be in any city on the planet in a matter of hours.

  • And once a virus touches down,

  • sometimes all it takes is one sneeze to spread

  • the infection throughout the community.

  • When humans were hunter-gatherers, roaming the wild savannas,

  • we were never in one place long enough,

  • and settlements were not large enough

  • to sustain the transmission of infectious microbes.

  • But with the advent of the agricultural revolution

  • 10,000 years ago, and the arrival of permanent settlements

  • in the Middle East, people began living side-by-side with animals,

  • facilitating the spread of bacteria and viruses

  • between cattle and humans.

  • Epidemics and pandemics come in many shapes and forms.

  • In 2010, for instance,

  • a devastating earthquake struck Haiti,

  • forcing thousands of people into temporary refugee camps.

  • Within weeks, the camps had become breeding grounds for cholera,

  • a bacteria spread by contaminated water,

  • triggering a country-wide epidemic.

  • But the most common cause of epidemics are viruses,

  • such as measles, influenza and HIV.

  • And when they go global, we call them pandemics.

  • Pandemics have occurred throughout human history,

  • Some have left scars on the tissue and bone of their victims,

  • while evidence for others comes from preserved DNA.

  • For instance, scientists have recovered DNA

  • from the bacteria that transmits tuberculosis

  • from the remains of ancient Egyptian mummies.

  • And in 2011,

  • scientists investigating a plague pit in the city of London

  • were able to reconstruct the genome of Yersinia pestis,

  • the bacterium responsible for the Black Death of the 14th century.

  • It is thought the plague originated in China

  • in around 1340,

  • spreading west along the Silk Road,

  • the caravan route running from Mongolia to the Crimea.

  • In 1347, the plague reached the Mediterranean,

  • and by 1400, it had killed in excess of

  • 34 million Europeans, earning it the title,

  • the Great Mortality.

  • It was later historians who called it the Black Death.

  • However, by far the greatest pandemic killer

  • is influenza.

  • Flu is constantly circulating between the Southern and Northern Hemispheres.

  • In North America and Europe,

  • seasonal flus occur every autumn and winter.

  • As the majority of children and adults will have been exposed to the virus in previous seasons,

  • these illnesses are usually mild.

  • However, every 20 to 40 years or so

  • the virus undergoes a dramatic mutation.

  • Usually this occurs when a wild flu virus

  • circulating in ducks and farm poultry

  • meets a pig virus, and they exchange genes.

  • This process is known as antigenic shift

  • and has occurred throughout human history.

  • The first recorded pandemic occurred in 1580.

  • The 18th and 19th centuries

  • saw at least six further pandemics.

  • In terms of mortality,

  • none can compare with the Great Flu Pandemic of 1918.

  • The first indication of the pandemic

  • came in the spring, when American troops in northern France

  • began complaining of chills, headaches and fever.

  • Then, the following September, at a U.S. Army barracks near Boston,

  • soldiers started collapsing on parade,

  • prompting their removal to the camp infirmary.

  • As a surgeon there recalled,

  • two hours after admission, they had the mahogany spots over the cheekbones

  • and a few hours later

  • you can begin to see the cyanosis extending from their ears

  • and spreading all over the face.

  • It is only a matter of a few hours then until death comes,

  • and it is simply a struggle for air until they suffocate.

  • On the S.S. Leviathan,

  • a huge American transport en route to Bordeaux,

  • sick men hemorrhaged blood from their noses,

  • turning the decks between their bunks slick with bodily fluids.

  • Meanwhile, British soldiers returning from northern France on furlough

  • introduced the flu to Dover and other Channel ports,

  • from where the virus was carried by rail to London.

  • By the time the pandemic had run its course

  • in April 1919,

  • an estimated 675,000 Americans

  • and 230,000 Britons were dead.

  • In India alone, some 10 million were killed,

  • and worldwide the death toll was an astonishing 50 million.

  • But that was then.

  • Today, planes can transport viruses

  • to any country on the globe

  • in a fraction of the time it took in 1918.

  • In February 2003, for instance,

  • a Chinese doctor arrived at the Metropole Hotel in Hong Kong

  • feeling unwell.

  • Unknown to him, he was harboring a new animal-origin virus called SARS,

  • short for Severe Acute Respiratory Syndrome.

  • Within 24 hours of checking into Room 913,

  • sixteen other guests had been infected,

  • and over the following days five boarded planes to overseas destinations,

  • spreading the virus to Vietnam, Singapore and Canada.

  • Flights between Hong Kong, Toronto and other international cities were quickly grounded

  • and thanks to other emergency measures,

  • a pandemic was averted.

  • By the time the outbreak was over four months later,

  • SARS had infected 29 countries worldwide

  • and more than 1,000 people were dead.

  • For all that the virus was rapidly contained, however,

  • there was little that could be done about the alarming news reports

  • carried by cable news channels and the Internet.

  • As bloggers added to the hysteria

  • by spreading unfounded conspiracy theories,

  • tourism in Hong Kong and other affected cities ground to a halt,

  • costing businesses more than 10 billion U.S. dollars.

  • One business, however, did very well.

  • Above all, SARS was a reminder that pandemics have always been associated with panic.

  • If history teaches us anything,

  • it's that while pandemics may start small,

  • their impacts can be as dramatic as wars and natural disasters.

  • The difference today

  • is that science gives us the ability to detect pandemics

  • right at the very beginning

  • and to take action to mitigate their impacts

  • before they spread too widely.

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B2 TED-Ed pandemic flu spreading sars spread

【TED-Ed】How pandemics spread - Mark Honigsbaum

  • 2014 187
    Zenn posted on 2013/04/07
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