COVID-19 attack rate increases with city size

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

is the (which was not peer-reviewed) The copyright holder for this preprint . Figure 1 : COVID-19 reported cases grow faster in larger cities. (a) Estimated exponential daily growth rates of COVID-19 in US Metropolitan Areas (MSAs). These estimates were made with the assumption that cities were experiencing exponential growth of cases. The growth rate of COVID-19 cases is approximately 2.4 times faster in New York-Newark-Jersey compared to Oak Harbour, WA (b) In the absence of effective controls, larger cities are expected to have more extensive epidemics than smaller cities, Eq. (1). Higher values of R result in a greater percentage of the population eventually infected, unless this effect is curbed by controls that reduce the social contact rate. The translation of growth rates into reproductive numbers was obtained using an infectious period of 1/γ = 4.5 days. These estimated values of R are high in some cases (e.g. New York City) compared to reports in other situations and may in part be the result of the acceleration of testing in larger cities and specific places.