I was listening to the Tom Holland The Rest is History podcast and apparently there was actual plague in the middle east just before Mohammed where up to 90% of some cities' populations died. Now they didn't understand how infection worked but those living outside the cities realised they weren't effected unless they went to the cities and then they were at risk. That's why they developed this idea that cities and civilisations were evil, decadent and disliked by God who wanted to punish them, while those caravan bandits were apparently moral and divinely favoured.

I wonder if any of those Taliban country boys will be hit with infections now they are in the big city and come to the same conclusions.