Have studies of the virus offered any clues to virulence ?

对病毒的研究是否为研究其毒性提供了一些线索？

There are two crucial factors : the transmissibility of the virus , and its virulence .

有两个关键因素：病毒的传播性和其毒性。

At the top of the list was the increased virulence of anti-japanese sentiment in modern china .

清单列举事项的首位是；现代中国人反日情感中增加了恶意的因素。

Though the h1n1 strain of the flu hasn 't increased in virulence , experts stress that h1n1 and influenza viruses in general remain unpredictable .

尽管甲型h1n1流感毒株的毒性尚未增强，但专家们强调，甲型h1n1流感和普通流感病毒总的来说仍是不可预测的。

Kawaoka 's team observed this virulence in mice and macaques as well , but pigs showed no outward signs of disease even though the virus reproduced capably in the swine respiratory system .

kawaoka的团队在小鼠和恒河猴中观察到类似强度的病毒毒性，但是尽管病毒能在猪的呼吸系统内有效的复制，猪却不会表现出明显的病症。