The reason is that the influenza virus mutates much more rapidly than most other viruses .

原因在于，流感病毒的变异比其它类型病毒的变异快得多。

The german question never dies . Instead , like a flu virus , it mutates .

对德国的质疑从未消失，只不过它像流感病毒一样变异了。

Malaria fears escalate as most dangerous mosquito mutates into two species

最危险的蚊子突变成两个种类，对于疟疾的担心上升

Imagine a killer virus , a bug that mutates so often that it inevitably finds a way to resist every drug .

想像一下，一个病毒杀手，一个变异如此频繁的小生物肯定会产生抵抗一切药物的能力。

If that virus mutates , the vaccines becomes useless , which is why people get the flu even when they get vaccinated .

如果病毒发生变异，研制的疫苗就会失效，所以即使注射了疫苗，人们还是会得流感。