The paper doesn't mention population density, but I'd think that would an important part of the story. Keeping infection rates at the same level in urbanized,

The paper doesn't mention population density, but I'd think that would an important part of the story. Keeping infection rates at the same level in urbanized, densely populated areas as is present in places where people live in more widespread, small agricultural communities seems like a pretty important deal. It's hard to imagine the larger Roman cities, and Rome itself, could exist without some manner of legal and technological organization to manage sanitation.