The virus stays in you longer because your body doesn't develop a way to fight it and kill it.

你的身体没有产生抵抗与杀死病毒的办法，因此病毒在你体内存活的时间更长了。

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Meanwhile, the deadliest strains of the virus perished with their hosts as natural selection favored strains that could infect hosts but not kill them.

同时，由于自然选择更倾向于选择那些能够感染宿主但不致其死亡的病毒，这种致命病毒便随着宿主的死亡而消失。

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So, either stimulates the production of-- and differentiation of B-cells, to produce a specific antibody that can neutralize the virus, or stimulates the production of cytotoxic T-cells that can kill infected cells within your body.

所以,疫苗的刺激要么能够,促进B淋巴细胞产生和分化,以生成特定的抗体来杀灭病毒,要么刺激T细胞释放细胞毒素,杀死身体里被感染的细胞

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Scientists want to flush out these so-called reservoirs and find a way to kill the virus for good.

MSN: Two more men with HIV now virus-free. Is this a cure?