  Most infectious diseases spread on a dynamic network of human interactions.
Recent studies of social dynamics have provided evidence that spreading
patterns may depend strongly on detailed micro-dynamics of the social system.
We have recorded every single interaction within a large population, mapping
out---for the first time at scale---the complete proximity network for a
densely-connected system. Here we show the striking impact of
interaction-distance on the network structure and dynamics of spreading
processes. We create networks supporting close (intimate network, up to ~1m)
and longer distance (ambient network, up to ~10m) modes of transmission. The
intimate network is fragmented, with weak ties bridging densely-connected
neighborhoods, whereas the ambient network supports spread driven by random
contacts between strangers. While there is no trivial mapping from the
micro-dynamics of proximity networks to empirical epidemics, these networks
provide a telling approximation of droplet and airborne modes of pathogen
spreading. The dramatic difference in outbreak dynamics has implications for
public policy and methodology of data collection and modeling.
