BACKGROUND: Implementing and lifting social distancing (LSD) is an urgent global issue of COVID-19 pandemic particularly when the travel ban is lifted to revive international business and economics. However, when and whether LSD can be considered is subject to the spread of SARS-COV-2, the recovery rate, and case-fatality rate. It is imperative to provide real time assessment of three quantities to guide LSD.
OBJECTIVE: A simple LSD index was developed for health decision-makers to do real-time assessment of COVID-19 at global, country, region, and community level.
METHODS: Data on the retrospective cohort of 186 countries with three quantities were retrieved from publicity available repository from January to early July. A simple index for guiding LSD measured by cumulative number of COVID-19 cases and recovery and case-fatality rate was envisaged. If the LSD index is less than 1 LSD can be considered. The dynamic changes of COVID-19 pandemic were evaluated to assess whether and when health decision-makers allow for LSD and re-implement social distancing after resurgence of epidemic.
RESULTS: After large-scale outbreaks in few countries before mid-March (pre-pandemic phase), the global weekly LSD index peaked at 4.27 in March and lasted until mid-June. (pandemic phase) during which most of countries were implicated and needed to take various social distancing measures. Since then, the value of LSD has gradually declined to 0.99 by July 5th. (post-pandemic phase) at which 64.7% countries/regions (120/186) had LSD <1 with the decile between 0 and 1 to refine risk stratification by countries. LSD index took about 115 days down to 1. We also presented the results of dynamic changes of LSD index for the globe and for each country/region with different time windows from January to July 5th. The results of LSD index on the resurgence of epidemic COVID-19 in certain regions and validation by other emerging infectious diseases are presented.
CONCLUSIONS: This simple LSD index provides a quantitative assessment of whether and when to ease or implement social distancing in order to provide the encompass for health decision-maker and traveler.