Those are due to mutations in avian and swine flu viruses.

来源: ZoyaWashington 于 2014-09-26 18:55:31 [] [旧帖] [给我悄悄话] 阅读数 : (27 bytes)
回答: 那禽流感和猪流感是咋回事？ 由 AtlasShrug 于 2014-09-26 13:18:17

Those are very rare cases.

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