英语语法分析

The virus has probably crossed over from simians into humans at least five times.

HIV可能在人类中和其他病毒至少混合过五次。

The ancestor virus - which, like many diseases, may have crossed into simians from another, still-unknown species - may have existed for millions of years.

这种病毒的祖先——像其他病毒一样，可能是其他病毒的混合体，仍是一种未知的病毒——可能几百万年前就存在了。