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Swine
flu Reports Human
nose too cold for bird flu viruses to thrive Washington:
A study authored by researchers at from Imperial College London and the University
of North Carolina has revealed that avian influenza viruses do not thrive in humans
because the temperature inside their noses is very low. The researchers say that
the new finding may help explain why bird flu viruses do not cause pandemics in
humans easily. In their study report, the scientists point out that there are
16 subtypes of avian influenza, some of which can mutate into forms that can infect
humans by swapping proteins on their surface with proteins from human influenza
viruses. They say that normal avian influenza viruses do not spread extensively
in cells at 32 degrees Celsius, the temperature inside the human nose, which is
probably because the viruses usually infect the guts of birds, which are warmer,
at 40 degrees Celsius. Based on this observation, according to them, it may be
said that avian flu viruses that have not mutated are less likely to infect people,
as the first site of infection in humans is usually the nose. When the researchers
created a mutated human influenza virus by adding a protein from the surface of
an avian influenza virus, they found it to struggle to thrive at 32 degrees Celsius.
This indicates that any mutated virus would have to undergo further changes to
adapt to the conditions in the human body. The
study also revealed that far fewer cells died as a result of infection with avian
influenza compared with human influenza at 32 degrees Celsius, supporting the
idea that the avian virus could not thrive at that temperature. Professor Wendy
Barclay, one of the authors of the study from the Division of Investigative Science
at Imperial College London, said: "Bird viruses are out there all the time but
they can only cause pandemics when they undergo certain changes. Our study gives
vital clues about what kinds of changes would be needed in order for them to mutate
and infect humans, potentially helping us to identify which viruses could lead
to a pandemic." Professor Barclay added: "It would be impossible to develop vaccines
against all 16 subtypes of avian flu, so we need to prioritise. By studying a
range of different viruses in systems like this one we can look for warnings that
they are already beginning to make the kinds of genetic changes in nature that
mean they could be poised to jump into humans; animal viruses that spread well
at low temperatures in these cultures could be more likely to cause the next pandemic
than those which are restricted." The study has been published in the journal
PLoS Pathogens. -May
15, 2009 Go
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