Travel Distance, Frequency of Return, and the Spread of Disease

Human mobility is a key driver of infectious disease spread. Recent literature has uncovered a clear pattern underlying thecomplexity of human mobility in cities: r· f , the product of distance traveled r and frequency of return f per user to a givenlocation, is invariant across space. This paper asks whether the invariant r· f also serves as a driver for epidemic spread, sothat the risk associated with human movement can be modeled by a unifying variable r· f . We use two large-scale datasets ofindividual human mobility to show that there is in fact a simple relation between r and f and both speed and spatial dispersion ofdisease spread. This discovery could assist in modeling spread of disease and inform travel policies in future epidemics--basednot only on travel distance r but also on frequency of return f .