An Index for Lifting Social Distancing During the COVID-19 Pandemic: Algorithm Recommendation for Lifting Social Distancing

Abstract

Background: Implementing and lifting social distancing (LSD) is an urgent global issue during the COVID-19 pandemic, particularly when the travel ban is lifted to revive international businesses and economies. However, when and whether LSD can be considered is subject to the spread of SARS-CoV-2, the recovery rate, and the case-fatality rate. It is imperative to provide real-time assessment of three factors to guide LSD.

Objective: A simple LSD index was developed for health decision makers to do real-time assessment of COVID-19 at the global, country, region, and community level.

Methods: Data on the retrospective cohort of 186 countries with three factors were retrieved from a publicly available repository from January to early July. A simple index for guiding LSD was measured by the cumulative number of COVID-19 cases and recoveries, and the case-fatality rate was envisaged. If the LSD index was less than 1, LSD can be considered. The dynamic changes of the COVID-19 pandemic were evaluated to assess whether and when health decision makers allowed for LSD and when to reimplement social distancing after resurgences of the epidemic.

Results: After large-scale outbreaks in a few countries before mid-March (prepandemic phase), the global weekly LSD index peaked at 4.27 in March and lasted until mid-June (pandemic phase), during which most countries were affected and needed to take various social distancing measures. Since, the value of LSD has gradually declined to 0.99 on July 5 (postpandemic phase), at which 64.7% (120/186) of countries and regions had an LSD<1 with the decile between 0 and 1 to refine risk stratification by countries. The LSD index decreased to 1 in about 115 days. In addition, we present the results of dynamic changes of the LSD index for the world and for each country and region with different time windows from January to July 5. The results of the LSD index on the resurgence of the COVID-19 epidemic 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 to provide advice for health decision makers and travelers.

Keywords: COVID-19; algorithm; data analysis; decision making; global health; index; pandemic; public health; social distancing.

Figure 1

Temporal trend of global lifting social distancing (LSD) index up to July 5, 2020. Overall: The LSD index ranged between 40.1 and 0.96 in the prepandemic period from January to mid-March. In the pandemic period from mid-March to June, the peak of the LSD index reached 4.27 on March 29. As of July 5, the LSD index declined to less than 1.

Figure 2

Temporal trend of global lifting social distancing (LSD) index up to July 5, 2020. A total of 66 countries with LSD≥1 on June 28 in the pandemic phase period. The social distancing was relaxed over 4 months.

Figure 3

Temporal trend of global lifting social distancing (LSD) index up to July 5, 2020. A total of 120 countries with LSD<1 on June 28 in the pandemic phase. Between March 13 and May 6, the LSD index was greater than 1. The time required for lifting social distancing was 55 days on average.

Figure 4

The number of countries and regions by ranges of the LSD index. As of July 5, 2020, the LSD index in 120 countries and regions was less than 1. The LSD index was greater than 1 in 66 countries and regions. LSD: lifting social distancing.

Figure 5

LSD index for severe acute respiratory syndrome outbreak in Taiwan, 2003. The 2.5 LSD index was high on March 22, 2003, at the initial epidemic stage then decreased to 0.3 on April 15, 2003. After April 22, the LSD index started increasing from 1 by nosocomial infection. The lower LSD index (<0.5) indicated that social distancing could have been lifted at the end of May. LSD: lifting social distancing.

Figure 6

LSD index for the Middle East respiratory syndrome–related coronavirus outbreak in South Korea, 2015. The LSD index greater than 6 was estimated on June 16, 2015. After about 2 weeks, the LSD index was less than 1 on July 1, 2015, and kept at a low value until the end of the outbreak. LSD: lifted social distancing.

Figure 7

LSD index for the Ebola outbreak in the Democratic Republic of the Congo, 2018. The LSD index was estimated as 11.7 at the initial stage on August 12, 2018. The LSD index never became less than one. LSD: lifting social distancing.