Half of the victims have been hospitalised, a high rate that may indicate an especially virulent strain of E. coli.
半数受害者都已住院，如此高的住院率表明这可能是一种毒性特别强的大肠杆菌菌株。
The authors argue the version of the disease that caused the medieval plague is likely extinct, but suggest that further study could reveal how it may have evolved into a less virulent strain.
作者们称引起中世纪瘟疫的品种可能已经灭绝了，但是他们认为进一步的研究可以揭示它是如何进化到一种没那么致命的类型。
Before 1997 WNV was not considered pathogenic for birds, but at that time in Israel a more virulent strain caused the death of different bird species presenting signs of encephalitis and paralysis.
在1997年以前，西尼罗河病毒并未被认为对鸟类具有致病性，但就在那时，以色列出现了一种能够导致多种鸟类出现脑炎和麻痹症状继而死亡的毒力更强的毒株。
Conclusion The infection of virulent strain of mouse poxvirus exists in experimental mice.
结论实验用昆明小鼠中存在鼠痘病毒强毒株感染。
In order to study the attenuation of neurovirulence of SA14 14 2 attenuated vaccine virus, monkeys and mice were tested with the strain and its parent SA14 virulent strain.
为了解乙型脑炎（乙脑）减毒活疫苗弱毒株SA14142神经毒力的减弱程度，本文对弱毒株及其原株SA14强毒株进行了猴体和小白鼠的致病性和病理学变化的比较试验。
In order to study the attenuation of neurovirulence of SA14 14 2 attenuated vaccine virus, monkeys and mice were tested with the strain and its parent SA14 virulent strain.
为了解乙型脑炎（乙脑）减毒活疫苗弱毒株SA14142神经毒力的减弱程度，本文对弱毒株及其原株SA14强毒株进行了猴体和小白鼠的致病性和病理学变化的比较试验。
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