re: #198 Citizen K
Look at their decision to not vaccinate those being held in these camps against influenza.
A bad strain of the flu - or some other viral outbreak - in such a tightly confined environment could easily lead to a significant death toll.
Bear in mind that Anne Frank wasn’t shot by some random SS Sturmmann, and she didn’t perish in a gas chamber; she died as the result of a typhus outbreak at Bergen-Belsen.