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等级:Senior
文章:384
积分:3400
门派:张家港
注册:2008-2-29 21:58:10 |
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 The Race Against Avian Flu
Public-health officials have been sounding the alarms, and now Washington has caught the bug. Meanwhile, scientists search for a vaccine.
In the calendar of natural calamities, flu season follows hurricane season, peaking in midwinter. Last week, with New Orleans still mostly uninhabitable, Washington was turning its attention to the threat posed by an exceptionally lethal strain of flu virus that could, in the worst case, kill as many people in a few months as AIDS has done in two decades. This time officials were resolved not to repeat the mistakes of Katrina, leaving the way open to make new mistakes. We now know better how to evacuate large cities—but how much good will that do in an emergency that calls for a quarantine instead?
At least no one could accuse the government of downplaying the threat: President Bush himself raised the possibility of using the military to contain a flu outbreak, while the Senate voted to spend $4 billion on preparations. Researchers have developed a promising vaccine that is now beginning large-scale production. But new fears arose last week when scientists announced they had reconstructed an actual living copy of the "Spanish flu" virus that killed 20 million to 50 million people in 1918. Apart from the implication that a terrorist could do the same thing, the disturbing news was that the culprit was essentially a bird virus which had undergone only "minimal changes to infect humans directly," according to microbiologist Terrence Tumpey of the Centers for Disease Control and Prevention. (More common, and less lethal, flu outbreaks are caused by germs that are a hybrid of mammalian and avian viruses.) As Tumpey points out, that is also a pretty accurate description of the H5N1 flu virus that has been circulating in Asia since 1997. (It is not related to the SARS outbreak of 2003.) In the last two years H5N1 has killed 140 million birds; it has infected just 116 people, mostly in Vietnam. But it was fatal to more than half of them. The critical difference from 1918 is that the newer virus is not ordinarily contagious between people. Almost everyone who has come down with it has caught it from a bird. So far.
We also have medical resources undreamed of in 1918. The resulting vaccine has been tested on 450 volunteers, and preliminary results are promising, at least for the highest doses tested; like many vaccines, it will probably have to be given in two shots, a month apart. On the assumption it will work, but also in part just to get a production line up and running, the government last month awarded a $100 million contract to Sanofi Pasteur of France, aiming for a stockpile of 20 million doses. The vaccine is tricky to manufacture, because it requires injecting virus into live chicken eggs; under a separate contract, the same company is researching a cell-based production system that could show results by the end of the decade.
The second line of defense against avian flu is antiviral drugs, in particular one called Tamiflu from the Swiss drugmaker Roche. It has shown good results against H5N1 in cell cultures and in mice, and it works against milder forms of the flu in humans, if they take it the first day or two after falling ill. if Tamiflu will work against avian flu, adding: "The disease goes so quickly to high levels of infection, you might need to take it before you get exposed."
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君子之过也，如日月之食也，过也，人皆见之；更也，人皆仰之！ |
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