虽然他在家中未饲养家禽，但是在他的居住区发现鸡和其它禽类。

While he did not keep poultry in his household, chickens and other birds were found in his neighbourhood.

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这些病毒对于野鸟通常无害或仅造成轻微感染。但对于密集环境下饲养的家禽，它们通常会造成比较严重的疾病。

In wild birds, most of these viruses are relatively harmless or cause only mild disease; however, in poultry, under crowded conditions, they can evolve to cause more severe disease.

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与在不同国家看到的家禽密度和饲养制度有关的因素也可影响发生人间病例的风险。

Factors relating to poultry densities and farming systems seen in different countries may also influence the risk that human cases will occur.

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