史密斯博士说这些虱子不会在他的系统树上出现，除非它们转变成寄生在胎盘类哺乳动物身上的物种，而大多数虱子不会经常变换宿主。

These lice would not show up in his tree, Dr. Smith said, unless they had been able to transfer to the placental mammalian species, and most lice do not regularly switch hosts.

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当HBV进入宿主细胞后，基因组转变为共价闭合环状dna (CCC - dna)。

Once HBV has entered the host cell, its genome is converted into a covalently closed circular DNA (CCC-DNA).

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