然而到了第二个冬季，病毒的N2蛋白发生突变因而无法被免疫系统识别。

By the second winter, however, the N2 part of the virus had also changed somewhat through mutations and was no longer very recognizable to the immune system.

youdao

然而到了第二个冬季，病毒的N2蛋白发生突变因而无法被免疫系统识别。

By the second winter, however, the N2 part of the virus had also changed somewhat through mutations and was no longer very recognizable to the immune system.

youdao