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

Published online by Cambridge University Press:  04 August 2022

Margaret R. Davies
Affiliation:
Department of Biostatistics, Epidemiology and Environmental Health Sciences, Jiann-Ping Hsu College of Public Health, Georgia Southern University, Statesboro, Georgia, USA
Xinyi Hua
Affiliation:
Department of Biostatistics, Epidemiology and Environmental Health Sciences, Jiann-Ping Hsu College of Public Health, Georgia Southern University, Statesboro, Georgia, USA
Terrence D. Jacobs
Affiliation:
Department of Biostatistics, Epidemiology and Environmental Health Sciences, Jiann-Ping Hsu College of Public Health, Georgia Southern University, Statesboro, Georgia, USA
Gabi I. Wiggill
Affiliation:
Department of Biostatistics, Epidemiology and Environmental Health Sciences, Jiann-Ping Hsu College of Public Health, Georgia Southern University, Statesboro, Georgia, USA
Po-Ying Lai
Affiliation:
Department of Biostatistics, School of Public Health, Boston University, Boston, Massachusetts, USA
Zhanwei Du
Affiliation:
Division of Epidemiology and Biostatistics, School of Public Health, LKS Faculty of Medicine, The University of Hong Kong, Hong Kong Special Administrative Region
Swati DebRoy
Affiliation:
School of Science and Mathematics, University of South Carolina Beaufort, Bluffton, South Carolina, USA
Sara Wagner Robb
Affiliation:
Department of Public Health Sciences, Clemson University, Clemson, South Carolina, USA
Gerardo Chowell
Affiliation:
Department of Population Health Sciences, School of Public Health, Georgia State University, Atlanta, Georgia, USA
Isaac Chun-Hai Fung*
Affiliation:
Department of Biostatistics, Epidemiology and Environmental Health Sciences, Jiann-Ping Hsu College of Public Health, Georgia Southern University, Statesboro, Georgia, USA
*
Corresponding author: Isaac Chun-Hai Fung, Email cfung@georgiasouthern.edu

Abstract

Introduction:

We aimed to examine how public health policies influenced the dynamics of coronavirus disease 2019 (COVID-19) time-varying reproductive number (Rt) in South Carolina from February 26, 2020, to January 1, 2021.

Methods:

COVID-19 case series (March 6, 2020, to January 10, 2021) were shifted by 9 d to approximate the infection date. We analyzed the effects of state and county policies on Rt using EpiEstim. We performed linear regression to evaluate if per-capita cumulative case count varies across counties with different population size.

Results:

Rt shifted from 2-3 in March to <1 during April and May. Rt rose over the summer and stayed between 1.4 and 0.7. The introduction of statewide mask mandates was associated with a decline in Rt (−15.3%; 95% CrI, −13.6%, −16.8%), and school re-opening, an increase by 12.3% (95% CrI, 10.1%, 14.4%). Less densely populated counties had higher attack rates (P < 0.0001).

Conclusions:

The Rt dynamics over time indicated that public health interventions substantially slowed COVID-19 transmission in South Carolina, while their relaxation may have promoted further transmission. Policies encouraging people to stay home, such as closing nonessential businesses, were associated with Rt reduction, while policies that encouraged more movement, such as re-opening schools, were associated with Rt increase.

Type
Original Research
Copyright
© The Author(s), 2022. Published by Cambridge University Press on behalf of Society for Disaster Medicine and Public Health

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