There are still some active smallpox virus specimens kept in the world, and there are two sources of small--two places where smallpox is stored now.

世界上仍有地方保存着,一些具有活性的天花病毒样本,有两个地方还储存着天花病毒样本

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Remember that the lucky thing about the smallpox vaccine was that a naturally occurring attenuated form of the smallpox virus variola called vaccinea was found.

对于天花病毒来说,幸运的是,存在一种自然发生的,被称作痘苗病毒的,天花病毒的衰减疫苗

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We know now that it's caused by a related virus, called vaccinia, remember the virus that causes smallpox is called variola.

我们现在知道这病由一种相关的病毒引起,这种病毒叫牛痘病毒,想想天花病毒也被叫做牛痘病毒

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And this is what's characteristic of smallpox, is that as the virus spreads through your body, it particularly, it particularly affects cells of your skin.

这是天花的特征,当病毒传遍全身时,它特别的,特别地作用于皮肤细胞

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This was not a naturally occurring attenuated virus as used in smallpox, but a virus that was attenuated in the laboratory, basically by propagating it in culture and looking for mutants that were formed as you propagated this virus under different experimental conditions.

这不是在制造天花疫苗时,使用的那种天然减毒病毒,而是一种在实验室中被人工弱化的病毒,基本上是通过在细胞中培养繁殖后,从这些培养出来的病毒中挑选出,不同实验环境下的变异体

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Smallpox is a virus called variola, it's a virus that contains DNA.

天花是病毒引起的,这种病毒含DNA

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