Exactly correct —I, too, read Alibek’s book with considerable consternation.
I vaguely remember that the Soviets had built the Sverdlvosk facility using plans captured from the Japanese Unit 731, who had a very advanced bio program there until being displaced by the invading Soviets.
In that incident they’d had been playing around with their most powerful strain of Anthrax:
The tech who had removed the filters did make a notation in the logbooks, but it went un-noticed by the supervisor in charge of the next shift of workers.
They simply turned all the fans with effectively no barrier to the outside world.
Across a nearby river from the lab was a ceramic factory crowded with innocent workers, and within a week all those who’d inhaled even the tiniest particles were all dead.
They blamed it all on “infected meat” or something.