Phone Data Show Stay-Home, Distancing Order Effects

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9 Sept. 2020. Anonymous data collected from millions of mobile phones last spring show stay-at-home and social distancing orders helped slow the spread of Covid-19 in the U.S. Findings from the study by researchers at University of Wisconsin in Madison appear in yesterday’s issue of JAMA Network Open, published by American Medical Association.

A team from UW’s Geospatial Data Science Lab analyzed data collected from more than 45 million smartphones and related mobile devices in March and April 2020, early in the U.S. pandemic, when some stay-at-home and social distancing mandates went into effect. The lab, led by geographic information scientist Song Gao, applies big data analytics to environmental and health issues related to geography.

In this study, Gao and colleagues used de-identified data from more than 45 million mobile phones, collected from 11 March to 10 April by commercial data research company SafeGraph. The researchers also accessed mobility data from the geospatial analytics service Descartes Labs, and geographic Covid-19 case data provided by Corona Data Scraper, an open-source service. The UW team looked primarily for associations of state-by-state rates of Covid-19 infections with changes in travel distances and time people stayed at home. In addition, the researchers measured the amount of time it took for Covid-19 case counts to double in a state, as a measure of disease spread.

The team found travel distances by phone users dropped sharply and home dwelling time increased across the U.S. after stay-at-home orders went into effect, particularly in states affected earlier in the pandemic, where those orders also went into effect earlier. Their analysis revealed those stay-at-home and social distancing orders are also associated with reduced spread of Covid-19 infections. Before the orders in some states, the median time for Covid-19 cases to double ranged from one to seven days. But after the orders went into effect, the median amount of time needed for case counts to double increased to a range of four to 30 days.

The researchers say the data show “stay-at-home social distancing mandates, when they were followed by measurable mobility changes, were associated with reduction in Covid-19 case rates.” And the authors conclude, “The findings come at a particularly critical period, when U.S. states are beginning to reopen their economies but Covid-19 cases are surging. At such a time, our study suggests the efficacy of stay-at-home social distancing measures and could inform future public health policy making.”

Using similar data, the Geospatial Data Science Lab provides an interactive map of the U.S., showing state and county-level mobility and home-dwelling time in response to the Covid-19 pandemic.

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