Abbreviation: COVID-19= coronavirus disease 2019.* Incidence= cases per 100,000 population calculated using 2019 US census population.† Large central metro: counties in metropolitan statistical areas (MSAs) of≥ 1 million population that 1) contain the entire population of the largest principal city of the MSA, 2) have the entire population contained in the largest principal city of the MSA, or 3) contain≥ 250,000 inhabitants of any principal city of the MSA; Large fringe metro: counties in MSAs of≥ 1 million population that did not qualify as large central metro counties; Medium metro: counties in MSAs of 250,000–999,999 population; Small metro: counties in MSAs of 50,000–249,999 population; Micropolitan: counties centered on an urban cluster with 10,000–49,999 population; Noncore: nonmetropolitan counties that did not qualify as micropolitan. https://www. cdc. gov/nchs/data_ access/urban_rural. htm# 2013_Urban-Rural_Classification_Scheme_for_Counties. § Data are provisional and subject to change.

Early in the pandemic, from mid-March to mid-May, COVID-19 incidence was highest among residents of large central and large fringe metropolitan areas. Beginning in mid-April, incidence in large metropolitan (central and fringe) areas declined and then increased similarly among all urban-rural areas. In September 2020, COVID-19 incidence sharply increased, and it remains highest among residents of medium/small metropolitan areas and micropolitan/noncore areas, indicating increased spread into rural communities. In October, weekly incidence was increasing steadily among all urban-rural areas.