I think it's the connection between hygiene level and spreading a contagion. What I've been thinking since watching it is, those folks must have massive antibodies built up by now. That would allow conscripted rural soldiers to survive as invaders, especially into societies with compromised immune systems, all else being equal. Dunno, I suspect there's a lot of learning from the CV-19 event that would give advantage if intentionally used this or next time around. Who needs "the bomb" now?
