COVID-19 attack rate increases with city size

Andrew J Stier; Marc G Berman; Luis M. A. Bettencourt

Accurately estimating the growth rate of epidemics is often difficult (17) , however, here we are concerned with the pattern of growth rates among cities rather than the precision of our growth rate estimates. To that end we additionally estimated the growth rate of COVID-19 cases by r = ln(cases T /cases 0 )/T which is an estimate of the slope of the line ln(cases) ∼ ln(a) + r · t from the first and last points of the time series (Supplementary Figure 4b) . These growth rate estimates showed a scaling relationship with city size that is consistent with Figure 1 of the main text. This was observed despite variations in growth rate estimates between the two methods Epidemic Models and the Reproductive Rate Even though well known, we include here the basic derivation of the reproductive rate and final size of the epidemic epidemic models, for the sake of completeness.