- It happened three times in the last century -- and nearly
happened again in 1997. Now experts say that another killer flu epidemic
is brewing.
-
- Will it emerge to kill millions -- as did the 1918
Spanish
flu? Or will it be nipped in the bud, as in the 1997 emergence of chicken
flu in humans? There are no easy answers. But now the same experts who
led the successful effort to stop the 1997 virus in Hong Kong raise
troubling
new questions.
-
- Those questions come from a report in the June 25 issue
of the prestigious Proceedings of the National Academy of Sciences. The
report shows that flu viruses similar to the killer 1997 strain reappeared
in Hong Kong in 2001. It happened again this year, the authors now
say.
-
- "We don't want this in humans or the world will
be in deep, deep trouble," researcher Robert G. Webster, PhD, tells
WebMD. "What will you do if one of these gets away? You haven't got
anything to do. Are we going to be prepared for this? It is going to happen
sooner or later, and authorities are not stockpiling effective drugs. We
have had two years of very mild flu, and now these drugs are in very short
supply. If one of these viruses gets away, we are in for
trouble."
-
- And while none of the 2001 or 2002 viruses infected
humans,
they had acquired dangerous new genes. Lab mice exposed to some of these
viruses quickly developed brain infections and died. Webster is director
of the World Health Organization collaborating center on influenza viruses
in lower animals and birds.
-
- Flu viruses can change their genes to become more
infectious
and more deadly to humans. The new study shows that the potentially deadly
Hong Kong flu virus known as H5N1 has been shifting in alarming
ways.
-
- "This time, this virus has picked up a whole set
of new internal genes," Webster says. "What worries me is this
shows it is possible for this virus to 'mate' with a number of different
viruses and produce viruses highly [lethal] for poultry. The key question
is, 'What is the potential in humans?' Can you afford to let the experiment
happen? The worrying thing is that all these original viruses continue
to circulate. If this virus mates with a virus that allows it to spread
from human to human, it would be of great worry to me."
-
- David L. Suarez, DVM, PhD, is lead scientist for avian
influenza at the U.S. Department of Agriculture's Southeast Poultry
Research
Laboratory in Athens, Ga. He's the point man for U.S. efforts to track
emerging flu epidemics in poultry.
-
- "There is danger of human infection -- the risk
is not zero," Suarez tells WebMD. "The major concern is that
the genes that made up the 1997 outbreak are still circulating.
Fortunately,
we haven't seen a virus with the same set of genes as in 1997, but the
fear is that we could always see something like that."
-
- Another author of the PNAS study is J.S. Malik Peiris,
MD, PhD, professor of microbiology at the University of Hong Kong. Peiris
points out that none of the H5N1 viruses seen since 1997 had the right
gene combination to let them infect humans.
-
- But Peiris also says that we should not be concentrating
solely on the H5N1 viruses as a possible cause of a global flu epidemic.
A number of other influenza viruses -- some more widespread than H5N1 --
also deserve close attention, he says.
-
- In 1997, Hong Kong authorities had all of the city's
3 million chickens slaughtered. While there were 18 human infections and
eight deaths, all of these infections came directly from birds. Killing
the poultry stopped the outbreak before the virus could learn to spread
from human to human. It was a close call -- and the first time a human
action prevented a worldwide epidemic.
-
- In 2001, Hong Kong authorities again ordered the deaths
of hundreds of thousands of chickens. They also established strict new
rules for the area's poultry farmers and live-poultry markets. Affected
chickens were killed this year, too, but a new poultry vaccine was used
to prevent spread among uninfected birds. Unfortunately, no such safeguards
are in place in mainland China.
-
- Mainland China is still denying they have a problem,
Saurez says. "For me it is a very big concern." Every year since
1997 we have seen flu viruses that cause severe disease -- the source for
which was China, he says. "It is there. So obviously they are unable
or unwilling to control it. It is a huge risk."
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- © 2002 WebMD Inc.
All rights reserved.
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- http://content.health.msn.com/content/article/1689.52862/content/article
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