LAUSR

The novel severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2) emerged in December 2019 and made a huge impact on human society. Different countries and regions have made different policies in control and prevention of the spread of SARS-CoV-2. It is known that the spread rate of a virus, i.e. SARS-CoV-2, heavily depends on population density. Besides, population density has large impacts on the basic reproduction number (R0) of SARS-COV-2. It is also observed that patients in high-transmission areas have a higher incidence of severe coronavirus disease outcomes when compared with patients in low-transmission areas. To this end, this study investigates the spread rates of SARS-CoV-2 in different regions with different population densities. We calculated the spread rates of SARS-CoV-2 in different regions of the USA. The counties of the USA are categorized into four regions: the first region consisting of counties with a population density <50 persons/km, and the second, third and fourth regions consisting of counties with population densities between 50 and 200, between 200 and 800, and >800 persons/km. In this way, the population of the USA is roughly evenly categorized into the four regions, which include 72.3, 91.2, 102.2 and 61.3 million persons, respectively. The spread rates of SARS-CoV-2 are calculated for each of the four regions. The calculations are based on the data collected by the data hub at the Johns Hopkins University from 1 March 2020 to 30 June 2020. The spread rate of SARS-CoV-2 in a region is defined as the average number of new deaths in last 7 days per 1 million persons as follows: