The Flu Virus Can not Be Foreseen There is a joke among flu researchers: " If you’ve seen one flu season, you’ve seen. . . o

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问题                     The Flu Virus Can not Be Foreseen
    There is a joke among flu researchers: " If you’ve seen one flu season, you’ve seen. . . one flu season." For those not up on epidemiological humor: the joke is wry commentary on the unpredictable nature of the flu virus. Every year it looks different,and every strain follows its own types. This is not just a coincidence that frustrates scientists-it’s the reason new strains like H1N1 are impossible to anticipate and fully prepare for.
    " I know less about influenza today than I did 10 years ago," quips Dr. Michael Oster-holm, director of the Minnesota Center of Excellence for Influenza Research and Surveillance and a former adviser to the U. S. Department of Health and Human Services. "Every stone we’ve turned over,we get more questions than we do answers."
    The flu returns every season and the world periodically experiences catastrophic pandemics, but epidemiologists still do not understand why some strains evolve to infect people and others do not;they are not entirely sure about how the flu is transmitted; nor do they understand why some patients become fatally ill while others develop minimal symptoms. As a result, when a new strain shows up—like H1N1—they often have little information to fall back on,and the lessons of previous pandemics are only somewhat helpful. While epidemiologists are still putting together a complete picture of H1N1, for example, its most striking difference with the seasonal flu is that the elderly are not the most vulnerable population. And when H1N1 does cause serious illness, patients develop different complications that are more difficult to treat than those with seasonal flu. "It’s a very different death," says Osterholm.
    The Centers for Disease Control currently maintains six different categories of flu-surveillance programs,but has rolled out new measures this year in order to monitor H1N1 ’s most worrying features. The backbone of its routine surveillance systems is not designed to count individual flu cases, but rather to get general indicators of how widespread the flu is and which strains are in circulation. " Influenza’s chimerical nature makes it a moving target for researchers," says Dr. Allison Aiello, assistant professor of epidemiology at the University of Michigan. " Even if we had complete seasonal flu data from the past, it wouldn’t necessary be helpful for a new strain of influenza," she explains.
Which of the following statements is TRUE according to the passage?

选项 A、Scientists have already known the reason why some strains infect people.
B、Now scientists know nothing about the transmission of flu virus.
C、People become fatally ill once they are infected by flu.
D、The previous information about flu provides limited help for scientists.

答案D

解析 事实细节题。第3段第1句话中作者提到:...the lessons of previous pandemics areonly somewhat helpful.说明以前的流行性疾病所提供的经验仅仅有一点帮助,也就是说其作用是有限的。
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