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2007-10-09 17:31 |
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题目:Bird flu and the deteriorating environment kbI:
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范文 l vM
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Earlier this year, bird flu panic was in full swing: The French B +`m
feared for their foie gras, the Swiss locked their chickens indoors, di
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and Americans enlisted prison inmates in Alaska to help spot CD +,&id
infected wild birds. kgEGL]G>
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The H5N1 virus - previously confined to Southeast Asia - was eg3zp gZ
striking birds in places as diverse as Germany, Egypt, and Nigeria, 8;5 UO,`T
and a flu pandemic seemed inevitable. /E2/
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Then the virus went quiet. Except for a steady stream of human cases vh"zYl`
in Indonesia, the current flu epicenter, the past year's worries JrQd7
about a catastrophic global outbreak largely disappeared. $"!"=v%B
What happened? 4hg#7#?boW
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Part of the explanation may be seasonal. Bird flu tends to be most R
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active in the colder months, as the virus survives longer at low +`r;3kH ..
temperatures. . 8<bz4
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"Many of us are holding our breath to see what happens in the (%rO'X
winter," said Dr. Malik Peiris, a microbiology professor at Hong H piP"Sl
Kong University. "H5N1 spread very rapidly last year," Peiris said. ; dPyhR
"So the question is, was that a one-off incident?" f\nF2rlu
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Some experts suspect poultry vaccination has, paradoxically, VC:.ya|Z
complicated detection. Vaccination reduces the amount of virus 5}x ^0
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circulating, but low levels of the virus may still be causing vrXUS9i.
outbreaks - without the obvious signs of dying birds. Y,RBTH
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"It's now harder to spot what's happening with the flu in animals *,.WI )@
and humans," said Dr. Angus Nicoll, influenza director at the h$)+$^YI
European Centres for Disease Control and Prevention. )@F uw*
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While the pandemic has not materialized, experts say it's too early IGeXj%e
to relax. )mT{w9u
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"We have a visible risk in front of us," said Dr. Keiji Fukuda, <t>"b|
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coordinator of the World Health Organization's global influenza p}$VBl$'
program. But although the virus could mutate into a pandemic strain, yANk(
Fukuda points out that it might go the other direction instead, ?B3
becoming less dangerous for humans. |j ($2.
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H5N1 has primarily stalked Asia. This year, however, it crossed the 8x#SpD
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continental divide, infecting people in Turkey, Iraq, Egypt, f'` QW@U
Djibouti, and Azerbaijan.
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But despite the deaths of 154 people, and hundreds of millions of ^iAOz-H
birds worldwide dying or being slaughtered, the virus still has not 6}zargu(;
learned how to infect humans easily. 'o;>6u<u
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Flu viruses constantly evolve, so the mere appearance of mutations [+<lm
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is not enough to raise alarm. The key is to identify which mutations W'WZ@ !!
are the most worrisome. \6~(#
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"We don't really know how many changes this virus has got to make to |zhV l
adapt to humans, if it can at all," said Dr. Richard Webby, a bird @k~'b
flu expert at St. Jude Children's Research Hospital in Tennessee.
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The most obvious sign that a pandemic may be under way will almost AG/?
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certainly come from the field: a sudden spike in cases suggesting sTeW4Hnp
human-to-human transmission. The last pandemic struck in 1968 - when d/oxRzk'L
bird flu combined with a human strain and went on to kill 1 million cYHHCaCS
people worldwide. fy&vo~4i;
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In May, on Sumatra island in Indonesia, a cluster of eight cases was 92zo+bc
identified, six of whom died. The World Health Organization h
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immediately dispatched a team to investigate. VE3,k'^v
The U.N. agency was concerned enough by the reports to put 7S+_eL^
pharmaceuticals company Roche Holding AG on standby in case its o ;nw;]oR
global antiviral stockpile, promised to WHO for any operation to .[YM0dt
quash an emerging pandemic, needed to be rushed to Indonesia. M;s r1C
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Luckily, the Sumatra cluster was confined to a single family. Though |-kU]NJFR
human-to-human transmission occurred - as it has in a handful of L<8:1/d\
other cases - the virus did not adapt enough to become easily Y*o T (
infectious. .C$4jR.KC
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This highlighted many of the problems that continue to plague public u17e
health officials, namely, patchy surveillance systems and limited G .PzpBA
virus information. T.m*LM
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Even in China, where H5N1 has circulated the longest, surveillance 0A$x'pU)
is not ideal. =Yd{PZ*fR
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"Monitoring the 14 billion birds in China, especially when most of PDwi] )6mf
them are in back yards, is an enormous challenge," said Dr. Henk |Dz$OZP
Bekedam, WHO's top official in China. Of the 21 human cases China bo>4 :i
has logged so far, 20 were in areas without reported H5N1 outbreaks d 5aG6/
in birds. Na6z 1&wS
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"We need to start looking harder for where the virus is hiding," V(/ @$&
Bekedam said. 8v e G ^o
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To better understand the virus' activity, it would help to have more @(k}q3b<
virus samples from every H5N1-affected country. But public health `TugtzRU
authorities are at the mercy of governments and academics. (f Gmjx
Scientists may hoard viruses while waiting for academic papers to be e
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published first. And developing countries may be wary of sharing 6.uyY@Yx
virus samples if the vaccines that might be developed from them D/& 8[Z/Cn
might ultimately be unaffordable. ar+ j`QIe
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That leaves public health officials with an incomplete viral Rv-`6eyAA
picture. P1gW+*?
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"It shouldn't just be WHO as a lonely voice in the desert, calling <FaF 67[Q
for more viruses (to be shared)," said Dr. Jeff Gilbert, a bird flu U- b(
expert with the Food and Agriculture Organization in Vietnam. All :>y?B!=
countries, need to understand that sharing will help them better blUnAu
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prepare for a flu pandemic, he said. ^( w %m#
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Though scientists are bracing themselves for increased bird flu r)4GH%+?fv
activity in the winter, there are no predictions about where it %3Ba9Nmid
might appear next. The WHO's Fukuda said it would not be a surprise ]RBT9@-:U
to see it appear in new countries.
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