Predictable county-level estimates of R0 for COVID-19 needed for public health planning in the USA

Ives, A. R.; Bozzuto, C.

The basic reproduction number, R0, determines the rate of spread of a communicable disease and therefore gives fundamental information needed to plan public health interventions. Estimated R0 values are only useful, however, if they accurately predict the future potential rate of spread. Using mortality records, we estimated the rate of spread of COVID-19 among 160 counties and county-aggregates in the USA. Among-county variance in R0 estimates was explained by four factors: the timing of the county-level outbreak, population size, population density, and spatial location. The high predictability of R0 makes it possible to extend estimates to all counties in the lower 48 States. The predictability also makes the R0 estimates valuable guides for designing long-term public health policies for controlling COVID-19.