(Don't mind the order of chapters; the content has been adjusted, leftover issues from the erroneous upload of chapter 137.)
It's impossible for a person to live their entire life in a sterilized environment. In fact, apart from the few hours you spend being wheeled into an operating room, you probably can't enjoy the benefits of a germ-free environment at all.
The reason human bodies can resist bacterial infections, aside from maintaining personal hygiene, is most importantly through physical exercise to enhance one's immune system.
Garrison Soldiers have an extremely high resistance to Knowledge Contamination and Echo Erosion, a kind of resistance akin to an immune system.
It's not that pollution and erosion don't exist, but that Garrison Soldiers have a stronger immunity than others.
However, this resistance, if relied upon solely by one's bodily senses, is very difficult to detect, and as such, it's easy to underestimate and be careless about it.
