She left so quickly because some virulent virus, only four days.

因为某种致命的病毒，只用了4天，她就走了。

youdao

The virus was proved to be a Duck Plague virus by means of cell culture, neutralization test and PCR assay, and it was maybe a virulent virus.

四川成都某鸭场分离得到一株疑似鸭瘟病毒，经细胞培养、中和实验、PCR鉴定，证明分离株为鸭瘟病毒，毒力测定及动物实验表明其可能为强毒株。

youdao

The results showed that the fusion protein can yield antibodies with high neutralizing activity as well as provide protection against challenge with virulent virus.

结果表明，用此融合蛋白的包涵体免疫豚鼠能诱导产生中和抗体，并对病毒的攻击提供免疫保护。

youdao

Angus Nicoll of the European Center for Disease Prevention says that at this point no one knows whether the virus will become more or less virulent in the months ahead.

VOA: standard.2009.04.30

In the Sabin vaccine, or the oral polio vaccine, now you have a non-virulent virus.

在沙宾疫苗,即口服小儿麻痹症疫苗中,存在非致病性病毒

耶鲁公开课 - 生物医学工程探索课程节选

The virus did not mutate to a more virulent form.

VOA: standard.2010.01.18

There are, after all, secrets to safeguard behind these doors, where virus experts scan virulent code, design cures and create advanced encryption systems.

CNN: Virus protection coming for wireless users