季节性流感来来去去(值得注意的是，美国20%以上的人口曾感染过)，一年又一年间，流感病毒已经悄悄发生了变化。

Seasonal influenza comes and goes (typically, it affects up to 20% of America's population), with the virus evolving slightly from one winter to the next.

youdao

季节性流感来来去去(值得注意的是，美国20%以上的人口曾感染过)，一年又一年间，流感病毒已经悄悄发生了变化。

Seasonal influenza comes and goes (typically, it affects up to 20% of America's population), with the virus evolving slightly from one winter to the next.

youdao