她推测到，这可能使他们对这种新的病毒产生一种免疫力，而年轻人则缺乏这种免疫。

That, she surmises, might give them an immunity to this new menace that young people lack.

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该病毒导致的疾病为“获得性免疫缺乏综合症”，即艾滋病，自从1981年被承认以来，已经杀死了3900万人，并且每年还要继续杀死150万人。

The disease it causes, acquired immunodeficiency syndrome, or AIDS, has killed 39m people since it was recognised in 1981, and continues to kill about 1.5m people a year.

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