单项选择题

案例分析题

While the world’s flu fighters have concentrated on countering the H1N1swine flu，bird flu H5N1has quietly continued to take its 【C1】______on both poultry and humans.Last year，17countries，【C2】______from Germany to Japan，reported outbreaks of H5N1in 【C3】______poultry and wild birds；and the World Health Organization，which still says H5N1causes a worldwide threat，recoded 72human 【C4】______，32of them fatal.
The major outbreak，entering its 【C5】______year，is still in the developing countries of Asia.Indonesia 【C6】______accounted for 19of the 32H5N1deaths；Vietnam，【C7】______5.But there are signs of 【C8】______.
The number of human deaths has been 【C9】______since peaking at 79in 2006.And fewer countries reported outbreaks in 2009than in 2008.
Partnership researchers compared notes on the effectiveness of control measures.Scientists reported that carefully 【C10】______killing can be just as effective as wide spread killing，and less 【C11】______.Others reported that reducing risk among those 【C12】______backyard poultry has to be a community-wide effort，since changing the practices of 【C13】______farmers has proven difficult.
In particular，Science Insider reported that a 3-year-old regional investigation network is making 【C14】______in sorting out the role of wild birds.Some water birds 【C15】______thought to be spreading the virus，such as the Asian open bill stork，are now known to quickly die of H5N1infection，Wiriyarat says.But pas serine species ，or perching birds，are apparently 【C16】______the virus without ill effects，says an Asian zoologist.He also adds that there is a high 【C17】______of outbreaks in poultry and passerine movements.
Wiriyarat says it is still 【C18】______what is causing the outbreak，whether there is a natural storage for H5N1，and how the virus is 【C19】______between domestic and wild birds.But while that research continues，the most effective way to reduce the amount of virus in 【C20】______is to control outbreaks in poultry，he says.

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