[drop|fall|die] like flies

(of a large number of people or animals) to die or get sick rapidly

The idiom "drop like flies" is indeed related to death, particularly signifying a high rate of casualties or deaths. It originates from the association of flies with unsanitary conditions and the rapidity with which they die in such environments.

In the war zone, soldiers were dying like flies in the fierce combat.
During the deadly pandemic, people in overcrowded areas were dropping like flies due to the fast-spreading virus.
The factory's unsafe conditions led to numerous accidents, with workers falling like flies.
When the natural disaster struck, poorly constructed houses were collapsing like flies, leading to significant loss of life.
In the midst of the shipwreck, passengers were drowning like flies, overwhelmed by the rough seas.