July 24, 2020

Association of Social Distancing, Population Density, and Temperature With the Instantaneous Reproduction Number of SARS-CoV-2 in Counties Across the United States

Category: Article Summary

Topic: Non-Pharmaceutical Interventions

• Ruben et al analyzed the effect of social distancing, population density, and temperature on effective reproduction number (Rt) in 211 counties in 46 US states and the District of Colombia (total population 178,892,208). Mean peak reduction in visits to non-essential businesses in early- to mid-April was 69% and a 50% decrease in such visits was associated with a 45% decrease in Rt. A 70% reduction in such visits brought 96% of such counties below Rt <1. Median case incidence and fatality rates were 10 times higher for the top decile of population density than for the lowest quartile (mean Rt in the first two weeks being 5.7 versus 3.1). Relative Rt decreased as temperatures warmed from 32°F to 52°F (O°C to 11°C), increased between 52°F and 68°F (11°C and 20°C), then again declined above 68°F (20°C).  

Rubin et al. (July 2020). Association of Social Distancing, Population Density, and Temperature With the Instantaneous Reproduction Number of SARS-CoV-2 in Counties Across the United States. JAMA Network Open. https://doi.org/10.1001/jamanetworkopen.2020.16099