Those people who had been chosen to be carriers were mostly people who were sickly and frail. As their bodies' constitution were weak, their resilience towards drugs and bacteria were not strong. Not long after they were injected with the bacteria, they would very soon die. Upon their deaths, that would be when the bacteria would spread, silently and unnoticed, as they achieved their evil objectives.
For the revered one to have the Clear Breeze City take in the frail elderly, weaker women and children continuously, his motives must be the same as that bacteria warfare, but just that the bacteria from Jun Wu Xie's past life had been replaced with a kind of drug that spread very easily, to achieve the same kind of effect. If what she thought was correct, those people who were made to ingest the medicine, must have been secretly sent to various places throughout the Lower Realm.