drop like flies バタバタと倒れる

drop like flies は人が次々と倒れていく様です。5:23 the same guys with strapped giant water jugs on their back, and they've wandered around filling you up, because people were dropping like flies. 大きな水筒を背負った男たちが砂漠の砂を均（なら）す作業員たちに水分を補給した。あまりの暑さのために作業員たちがバタバタと倒れたからだ。

The Making of Stargate 1994 Movie Documentary

https://www.youtube.com/watch?v=bIRnF4svMZ0  1:04 they seem to be dropping like flies. 今回の大統領選では候補者たちが次々と病気にかかっている。
Why Presidential Candidates on the Campaign Trail Seem To Be Getting Sick

練習問題解答
a-3991 dropping like flies
a-5821 dropping like flies
a-7854 dropping like flies
a-9089 dropping like flies
b-5542 dropping like flies