The result demonstrated that the immune selective pressure only had selective function, but not the creating - mutation function in the mutation of virus.

本研究结果显示，抗体这一免疫压力在病毒的变异中可能只起选择性作用，而不起促进变异的作用。

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The World Health Organisation said this week it had found no evidence of mutation in the virus that had caused the latest Indonesian deaths.

ECONOMIST: Down with the flu | The

The reason for that is that the influenza virus has a rapid rate of mutation, forcing companies that manufacture the vaccine to make their best guess as to which flu types will be more prevalent in a given season.

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