어서 사라지다

disappear as a result of that

An "-아서/-어서" clause naming the cause or the elapsed time, plus 사라지다 "disappear, vanish". The lines cover a species dying out over decades, food debris that brushing alone doesn't get rid of, something presumed gone once immunity was acquired, and people being loaded into a van and vanishing. It also does simple duration — it disappears in a bit under a month. 사라지다 is the thing going by itself; making it go is 없애다.