Epidemics in Venice: on the small or large nature of the pre-modern world

Marvel et al. [12] recently argued that the pre-modern contact world was physically and, by set inclusion, socially not small-world. Since the Black Death and similar plagues used to spread in well-defined waves, the argument goes, the underlying contact network could not have been small-world. I counter here that small-world contact networks were likely to exist in pre-modern times in a setting of the greatest importance for the outbreak of epidemics: urban environments. I show this by running epidemic diffusion simulations on the transportation network of Venice, verifying how such network becomes small-world when we account for naval transportation. Large epidemic outbreaks might not have been even possible without the catalyst of urban small-worlds.