Spatially refined time-varying reproduction numbers of SARS-CoV-2 in Arkansas and Kentucky and their relationship to population size and public health policy, March – November, 2020

Abstract

Purpose: To examine the time-varying reproduction number, Rt, for COVID-19 in Arkansas and Kentucky and investigate the impact of policies and preventative measures on the variability in Rt. Methods: Arkansas and Kentucky county-level COVID-19 cumulative case count data (March 6-November 7, 2020) were obtained. Rt was estimated using the R package 'EpiEstim', by county, region (Delta, non-Delta, Appalachian, non-Appalachian), and policy measures. Results: The Rt was initially high, falling below 1 in May or June depending on the region, before stabilizing around 1 in the later months. The median Rt for Arkansas and Kentucky at the end of the study were 1.15 (95% credible interval [CrI], 1.13, 1.18) and 1.10 (95% CrI, 1.08, 1.12), respectively, and remained above 1 for the non-Appalachian region. Rt decreased when facial coverings were mandated, changing by -10.64% (95% CrI, -10.60%, -10.70%) in Arkansas and -5.93% (95% CrI, -4.31%, -7.65%) in Kentucky. The trends in Rt estimates were mostly associated with the implementation and relaxation of social distancing measures. Conclusions: Arkansas and Kentucky maintained a median Rt above 1 during the entire study period. Changes in Rt estimates allows quantitative estimates of potential impact of policies such as facemask mandate.

SARS-CoV-2 Transmission Potential and Policy Changes in South Carolina, February 2020 – January 2021

“…40 Politis et al found that after school reopened, R t increased by 12% and 9% in Arkansas and Kentucky, respectively. 10 Thus, our findings in South Carolina are consistent with findings in other states in general, that school re-opening in August and September 2020 was associated with increased SARS-CoV-2 transmission as evidenced in an increase in R t .…”

“…40 Politis et al found facemask mandate was associated with a decrease in R t by 11% and 6%, respectively, in Arkansas and Kentucky. 10 Thus, our findings in South Carolina are consistent with findings in other states that a mask mandate was associated with slowing epidemic growth.…”

SARS-CoV-2 transmission potential and rural-urban disease burden disparities across Alabama, Louisiana, and Mississippi, March 2020 — May 2021

“…Meanwhile, rural-urban disparities was generally not observed in the Appalachian region of Kentucky and both Delta and non-Delta regions of Arkansas over much of 2020. [33] In a study of 5 Western states, [41] North Dakota was the only state where densely populated counties consistently had a higher per-capita cumulative incidence throughout 2020. Rural counties in Louisiana and Mississippi continued to experience a higher burden in the first half of 2021.…”

“…A negative slope indicates that counties with lower population size were associated with higher case burden while a positive slope means the opposite (Text S1). [ 32 , 33 ] Time variability was assessed by regressing data at four time points (Date of report: June 17, 2020, October 17, 2020, February 17, 2021, and May 17, 2021).…”

SARS-CoV-2 Transmission Potential and Policy Changes in South Carolina, February 2020 – January 2021

“…8 This makes R t a better measure of disease spread over time as populations put interventions into effect. 9,10 Public health policies regarding non-pharmaceutical interventions (NPIs) have been examined for their impact on the R t . 11 South Carolina put various policies into place from March 16, 2020, through October 5, 2020, primarily in the form of executive orders.…”