what is the meaning of "Dropping like flies" I need both English and Chinese.

剑桥词典(Cambridge Dictionary):

[1] If people are dropping like flies, they are dying or falling down in large numbers: (像苍蝇落下)

死了很多人；跌了很多人...

[a] The heat was overwhelming and people were dropping like flies.

[2] to stop doing an activity in large numbers:

[a] There used to be over 20 of us in our aerobics class but they're dropping like flies.(像苍蝇落下)很多人停止做活动...