On present understanding, H5 and H7 viruses are introduced to poultry flocks in their low pathogenic form.

据目前所知，H5和H7型病毒以低致病形式传给禽类。

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It spreads very rapidly through poultry flocks, causes disease affecting multiple internal organs, and has a mortality that can approach 100%, often within 48 hours.

它在禽类中传播非常迅速，感染多个内脏器官，通常在48小时内，死亡率可达到100%。

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On a more sobering note, the report notes that avian flu is now endemic in the poultry flocks of many countries in the region and indeed has spread to Europe and central Asia.

报告以一种使人清醒的口气指出，禽流感目前在东亚很多国家的禽类中流行，并确实已传播到欧洲和中亚。

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Since first emerging in 1997 in Hong Kong, the bird flu has spread across poultry flocks in nine East Asian countries.

FORBES: A Killer Virus Spreads

In some places, at least, ruthless monitoring of poultry flocks has reduced both the avian disease and the (already rare) cases of people becoming infected.

ECONOMIST: Bird flu and public health

The countries represented at the summit pledged a co-ordinated fight against the disease and issued a declaration that mass culling of infected poultry flocks was the best way to control its spread.

ECONOMIST: Averting a global plague | The