Avian flu. We all heard about it on T.V, it killed bird in Turkey
and everyone talks about the fear that it mite attack human
and will become a plague.
But what do you really know about the avian flu?
Well hear are a few things that you might like to know about
the avian flu.
Influenzavirus A is a genus of a family of viruses called
orthomyxoviridae in virus Classification . Influenzavirus A has
only one species in it; that species is called "influenza A virus".
Influenza A virus causes "avian influenza" (also known as bird
flu, avian flu, influenzavirus A flu, type A flu, or genus A flu).
It is hosted by birds, but may infect several species of
mammals. All known subtypes are endemic in birds. It was first
identified in Italy in the early 1900s and is now known to exist
worldwide.
The avian flu virus subtypes are labeled according to an H
number (for hemagglutinin) and an N number (for
neuraminidase ). Each subtype virus has mutated into a variety
of strains with differing pathogenic profiles; some pathogenic
to one species but not others, some pathogenic to multiple
species. Most known strains are extinct strains. For example,
the annual flu subtype H3N2 no longer contains the strain that
caused the Hong Kong Flu.
Human influenza virus:
"Human influenza virus" usually refers to those subtypes that
spread widely among humans. H1N1, H1N2 and H3N2. are the
only known avian flu virus subtypes currently circulating among
humans.
In humans, avian flu viruses cause similar symptoms to other
types of flu These include fever, cough , sore throat, muscle
aches, conjunctivitis and, in severe cases, severe breathing
problems and pneumonia that may be fatal. The severity of the
infection will depend to a large part on the state of the
infected person's immune system and if the victim has been
exposed to the strain before, and is therefore partially
immune. In one case, a boy with H5N1 experienced diarrhea
followed rapidly by a coma without developing respiratory or
flu-like symptoms, suggesting non-standard symptoms.
The avian influenza subtypes that have been confirmed in
humans ordered by the number of known human deaths, are:
H1N1 caused "Spanish flu", H2N2 caused "Asian Flu", H3N2
caused "Hong Kong Flu", H5N1 is the current pandemic threat,
H7N7 has unusual zoonotic potential.
H1N1:
A variant of H1N1 was responsible for the Spanish flu
pandemic that killed some 50 million to 100 million people
worldwide over about a year in 1918 and 1919.
H2N2:
The Asian flu was a pandemic outbreak of H2N2 avian influenza
that originated in Chaina in 1957, spread worldwide that same
year during which a flu vaccine was developed, lasted until 1958
and caused between one and four million deaths.
H3N2:
H3N2 evolved from H2N2 by antigenic shift and caused the
Hong Kong Flu pandemic of 1968 and 1969 that killed up to
750,000.
H5N1:
H5N1 is a highly pathogenic form of avian influenzavirus. Since
1997 , outbreaks of H5N1 flu have caused the death or culling
of tens of millions of birds. Over 100 people have been
infected by H5N1, with a mortality rate of over 50%. H5N1
has been the focus of much concern amid warnings that the
H5N1 strain will likely evolve into a form that causes a global
human pandemic with a very high mortality rate. As of
November 1, 2005 , 184 cases of infections in humans,
resulting in 85 deaths, have been confirmed outside of China.
H7N7:
H7N7 has unusual zoonotic potential. In 2003 in Netherlands
89 people were confirmed to have H7N7 influenza virus
infection following an outbreak in poultry on several farms. One
death was recorded.