Cell Phone Location Data Can Identify Areas of COVID-19 Spread

County-level cell phone location data could enable public health officials to better monitor adherence to stay-at-home guidelines, as well as estimate the future spread of COVID-19, according to a study published in JAMA Internal Medicine.

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Currently, there is little evidence to support cell phone location data as a marker of decline in growth rate of COVID-19 cases, the research team noted. While this information showed reductions in cell phone activity at workplace and retail locations, it was not known whether these data correlate with the spread of COVID-19 in a given region.

Researchers analyzed anonymous, county-level cell phone location data, publicly available via Google, and incidence of COVID-19 for more than 2,500 US counties between January and May 2020. The group adjusted the data for multiple county- and state-level characteristics, including population density, obesity rates, state spending on healthcare, and other factors.

Researchers then looked at the change in cell phone use in six categories of places over time: workplace, retail locations, transit stations, grocery stores, parks, and residences.

The location data showed marked reductions in cell phone activity in public places with an increase in activity in residences even before stay-at-home advisories were rolled out. Additionally, the data showed an increase in workplace and retail location activity as time passed after stay-at-home advisories were implemented, indicating waning adherence to the orders over time – information that could be particularly helpful at the public health level.

These findings are among the first to demonstrate that cell phone location data can help public health officials better monitor adherence to stay-at-home guidelines, as well as help identify areas at greatest risk for rapid COVID-19 spread.

"This study demonstrates that anonymized cell phone location can help researchers and public health officials better predict the future trends in the COVID-19 pandemic," said corresponding author Shiv T. Sehra, MD, Director of the Internal Medicine Residency Program at Mount Auburn Hospital.

"To our knowledge, our study is among the first to evaluate the association of cell phone activity with the rate of growth in new cases of COVID-19, while considering regional confounding factors."

Notably, the study also revealed that urban counties with higher populations and a higher density of cases saw a larger relative decline in activity outside place of residence and a greater increase in residential activity.

“Perhaps the most important observation of this study was that a decrease in activity at the workplace, transit stations, and retail locations and an increase in activity at the place of residence was associated with a significant decline in COVID-19 cases at five, ten, and 15 days,” researchers said.

“The immediate implication of these results is that it supports the use of cell phone data as a measure of adherence to stay-at-home advisories and may act as a prognostic measure that may help to identify areas at greatest risk for more rapid growth of the epidemic.”

Cell phone data has helped researchers understand the spread of COVID-19 and anticipate future trends throughout the pandemic. In July, a team from Colorado State University used cellular wireless network data to pinpoint potential hotspots for COVID-19 transmission.

“Our findings could help risk managers with planning and mitigation,” said Edwin Chong, professor of electrical and computer engineering at Colorado State University. “It might prompt them to cordon off a busy plaza, for example, or implement stricter social distancing measures to slow the spread of the virus.”

Researchers from the current JAMA study stated that their results could help public health officials better monitor and predict COVID-19 spread.

"Some of the factors affecting cell phone activity are quite intuitive," said Sehra, who is also an Assistant Professor of Medicine at Harvard Medical School. "But our analysis helps demonstrate the use of anonymous county-level cell phone location data as a way to better understand future trends of the pandemic. Also, we would like to stress that these results should not be used to predict the individual risk of disease at any of these locations."