Abstract
The spread of pandemics such as COVID-19 is strongly linked to human activities. The objective of this article is to specify and examine early indicators of disease spread risk in cities during the initial stages of outbreak based on patterns of human activities obtained from digital trace data. In this study, the Venables distance (Dv) and the activity density (Da) are used to quantify and evaluate human activities for 193 United States counties, whose cumulative number of confirmed cases was greater than 100 as of March 31, 2020. Venables distance provides a measure of the agglomeration of the level of human activities based on the average distance of human activities across a city or a county (less distance could lead to a greater contact risk). Activity density provides a measure of level of overall activity level in a county or a city (more activity could lead to a greater risk). Accordingly, Pearson correlation analysis is used to examine the relationship between the two human activity indicators and the basic reproduction number in the following weeks. The results show statistically significant correlations between the indicators of human activities and the basic reproduction number in all counties, as well as a significant leader-follower relationship (time lag) between them. The results also show one to two weeks’ lag between the change in activity indicators and the decrease in the basic reproduction number. This result implies that the human activity indicators provide effective early indicators for the spread risk of the pandemic during the early stages of the outbreak. Hence, the results could be used by the authorities to proactively assess the risk of disease spread by monitoring the daily Venables distance and activity density in a proactive manner.
Highlights
The objective of this study is to reveal and evaluate early indicators of human activity during COVID19 period in cities at the initial stages of the outbreak using measures of human activities derived from digital trace data
We examined the correlation between the two human activity indicators and the basic reproduction number across all counties
We showed that the average distance between human activities (Dv) increased by 10%–15%, and the average human activity intensity (Da) decreased by 5%–10% for social tiles during March 2020 compared with the baseline period of January 2020
Summary
The objective of this study is to reveal and evaluate early indicators of human activity during COVID19 period in cities at the initial stages of the outbreak using measures of human activities derived from digital trace data. While reduction in human activities is considered an effective measure for containing epidemics and pandemics, there are limited reliable, proven, real-time leading indicators related to human activities that could provide early insights about the risk of disease spread in a region to inform proactive policy making. One reason for this limitation has been the absence of quantitative measures and data that could be examined to proactively evaluate human activities. Two of the most important aspects of human activities during an epidemic are agglomeration of activities and intensity of activities
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