The science of virusesvirology


Avian Flu History

Avian influenza virus usually refers tohuman-to-human transmission evolves, the
influenza A viruses found mainly in birds,disease could spread around the globe in days
but infections can occur in humans. The riskthrough modern jet travel by infected
is generally low to most people, because thepersons.
viruses do not usually infect humans.
However, confirmed cases of human infectionThe current bird flu, a strain known as H5N1,
have been reported since 1997, and theclearly can be transmitted directly from
current outbreak of bird flu worldwidepoultry to people. Most cases have been
increases the risk that the virus will mutatetraced directly to contact with sick birds,
into a form which can be spread person toalthough human-to-human transmission appears
person.to have occurred in at least one instance.
H5N1 first appeared in Hong Kong in 1997, and
All flu viruses are thought to haveas of July 26, 2006 there have been 232 cases
originated in birds. But scientists also haveof flu worldwide, mostly in Southeast Asia,
long believed that in order to cause humanaccording to the World Health Organization.
epidemics, the viruses first had to spreadMortality has been greater than fifty
from birds to pigs, where genetic changespercent. These figures include only patients
occur which allow the viruses to spread morewhose diagnosis has been confirmed by lab
easily in mammals. Flu strains that are moretests. Cases of severe illness or death are
birdlike are more dangerous to humans becausemost likely to be diagnosed and reported,
their immune systems have not been exposed towhile milder cases go undiagnosed and
them  before.unreported; therefor it is difficult to know
the  true  mortality  rate  from  H5N1.
It is thought that the deadly 1918 flu
epidemic, which killed 20 to 40 millionDue to the fact that most cases are occurring
people, derived from bird flu. Known asin third-world countries where health
"Spanish Flu" or "La Grippe," the influenzaservices and reporting are poor, the actual
pandemic of 1918-1919 was a global disaster,number is likely much higher than the
and it has been cited as the most devastatingofficial count. Masato Tashiro, head of
epidemic in recorded world history. Morevirology at the Tokyo National Institute of
people died from influenza in a single yearInfectious Disease, gave a presentation at a
than in four years of the Black Death orvirology conference in Marburg, Germany, on
Bubonic  Plague  from  1347  to  1351.November 19, 2005 about unofficial bird flu
tallies from China. He listed "several dozen"
Obviously, it is of vital importance thathuman outbreaks, nearly 300 deaths, 3000
bird flu be contained, and that any infectedpeople quarantined, and seven human-to-human
birds are culled. It would only require atransmissions. The meeting was reported in
handful of mutations in order for H5N1 avianthe German newspaper Frankfurter Allgemeine
flu to become a pandemic virus like the oneZeitung.
which spread around the world in 1918. Once



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