Flu viruses circulate around the world throughout the year but a flare up in the U.S. is most common in the fall and winter hitting it's worst point between December and February according to the Centers for Disease Control.
根据疾控中心的数据,流感病毒全年都在全世界范围内传播,在美国,秋冬季节的流感爆发最为严重,12月至次年2月是最高峰。