Fig. 2. Connectivity and uncertainty reduction across 35 US states.

a The adjacency matrix for 35 US states. Adjacent states are highlighted by blue squares. b Numbers of commuters among 35 US states from the 2010 census survey. Color shows the logarithmic-transformed (base 10) commuting population from resident (x-axis) to work (y-axis) locations. Surveillance data from one state (x-axis) can reduce the uncertainty of infected (c) and susceptible (d) populations in other states (y-axis). Color indicates the reduced fraction of variance for infected and susceptible populations (u^I and u^S). Results are averaged over data assimilation during nine seasons.