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Tiny Change Can Make Flu Virus Deadly, Scientists Say
By RANDOLPH E. SCHMID
.c The Associated Press
WASHINGTON (Sept. 6) - A tiny change in a virus that causes flu can turn it
from an unpleasant annoyance to a killer, a team of researchers has found.
A change in just one of the virus' 10 genes switched a form of flu in
chickens to a strain deadly to humans four years ago in Hong Kong, they
discovered.
Authorities were forced to kill more than a million chickens in that city to
block spread of the flu, which killed six of the 18 humans that it infected.
''What this tells you is that the avian influenza virus can become the virus
that causes the disease in humans at any moment,'' said Yoshihiro Kawaoka,
one of the research team at the University of Wisconsin-Madison.
The findings are published in Friday's issue of the journal Science.
''We have found that a limited number of very tiny genetic changes in a
specific gene, one called PB2, can have a big effect on how potent the
influenza virus is,'' said Kawaoka.
''Because the influenza virus constantly mutates, and because only a few
changes can make a nonpathogenic virus highly pathogenic, we should assume
that an outbreak of any new strain or subtype is potentially dangerous to
humans,'' he said.
Robert Lamb, professor of biochemistry at Northwestern University, called the
report intriguing.
''In many ways it tells us just how complicated understanding the influenza
virus is, that a point mutation in one gene can confer virulence,'' he said.
''It also tells us just how dangerous a virus influenza is.''
The disease reappeared in Hong King this summer and more than a million
chickens again were slaughtered.
It has long been known that animals such as swine can harbor viruses, with
major epidemics occurring when it jumps from the usual host to humans. The
Hong Kong case was the first documented instance of a flu virus jumping
directly from chickens to humans, according to the National Institutes of
Health.
The jump from fowl to humans raises particular worries because of the many
live poultry markets common around the world, including parts of Florida and
New York, Kawaoka said.
Viruses need to enter the cells of their hosts to reproduce and spread. Their
surfaces are key to this ability, and the surface proteins of flu viruses
change readily to escape detection by the human immune system. That is why
new flu vaccines have to be developed each year.
The Wisconsin team's report also indicates that small changes can transform a
disease generally confined to the respiratory system to one that infects the
vital organs including the heart and brain.
The team tested various forms of the Hong Kong virus, known as H5N1 influenza
A, in mice.
They obtained samples of the viruses that had infected Hong Kong humans
during the 1997 outbreak and divided them into two types, one that merely
made mice sick and another that was deadly.
Then the researchers were able to study the viruses by swapping genes between
them and testing how they affected mice. Through that process they discovered
that the gene called PB2 from the harmful group gives the virus its potency.
Further testing allowed them to identify the changes in the gene that had the
effect.
While not all the effects of the PB2 gene are known, scientists think it
directs the production of an enzyme that helps force the host cell to make
more viruses.
Dr. Anthony Fauci, director of the National Institute of Allergy and
Infectious Disease, which supported the research, said the study ''provides
insight into the emergence of virulent viruses and can help us develop better
strategies for detecting future outbreaks.''
AP-NY-09-06-01 1401EDT
Copyright 2001 The Associated Press. The information contained in the AP news
report may not be published, broadcast, rewritten or otherwise distributed
without the prior written authority of The Associated Press. All active
hyperlinks have been inserted by AOL.
"Never cease in the fight for peace, justice, and equality for all people. Be
persistent in all that you do and don't allow anyone to sway you from your
conscience.".....Leonard Peltier
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