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Population mobility reductions associated with travel restrictions during the Ebola epidemic in Sierra Leone: use of mobile phone data

Population mobility reductions associated with travel restrictions during the Ebola epidemic in Sierra Leone: use of mobile phone data
Population mobility reductions associated with travel restrictions during the Ebola epidemic in Sierra Leone: use of mobile phone data

Background: Travel restrictions were implemented on an unprecedented scale in 2015 in Sierra Leone to contain and eliminate Ebola virus disease. However, the impact of epidemic travel restrictions on mobility itself remains difficult to measure with traditional methods. New 'big data' approaches using mobile phone data can provide, in near real-time, the type of information needed to guide and evaluate control measures.

Methods: We analysed anonymous mobile phone call detail records (CDRs) from a leading operator in Sierra Leone between 20 March and 1 July in 2015. We used an anomaly detection algorithm to assess changes in travel during a national 'stay at home' lockdown from 27 to 29 March. To measure the magnitude of these changes and to assess effect modification by region and historical Ebola burden, we performed a time series analysis and a crossover analysis.

Results: Routinely collected mobile phone data revealed a dramatic reduction in human mobility during a 3-day lockdown in Sierra Leone. The number of individuals relocating between chiefdoms decreased by 31% within 15 km, by 46% for 15-30 km and by 76% for distances greater than 30 km. This effect was highly heterogeneous in space, with higher impact in regions with higher Ebola incidence. Travel quickly returned to normal patterns after the restrictions were lifted.

Conclusions: The effects of travel restrictions on mobility can be large, targeted and measurable in near real-time. With appropriate anonymization protocols, mobile phone data should play a central role in guiding and monitoring interventions for epidemic containment.

0300-5771
1562-1570
Peak, Corey M.
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Wesolowski, Amy
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Zu Erbach-Schoenberg, Elisabeth
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Tatem, Andrew J.
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Wetter, Erik
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Lu, Xin
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Power, Daniel
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Weidman-Grunewald, Elaine
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Ramos, Sergio
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Moritz, Simon
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Buckee, Caroline O.
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Bengtsson, Linus
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Peak, Corey M.
938c4ee6-0696-48c0-b453-a9d22c3f9457
Wesolowski, Amy
343b0df8-5a2f-46e2-9f1c-001d4adf7fb1
Zu Erbach-Schoenberg, Elisabeth
9a1f59b2-c661-42c9-ad94-96772c292add
Tatem, Andrew J.
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Wetter, Erik
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Lu, Xin
a681bac0-d6d1-4e8e-a642-4ce42ae2cc9d
Power, Daniel
bed78a64-4f2c-44f6-9ca8-8c4a133c4b49
Weidman-Grunewald, Elaine
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Ramos, Sergio
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Moritz, Simon
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Buckee, Caroline O.
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Bengtsson, Linus
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Peak, Corey M., Wesolowski, Amy, Zu Erbach-Schoenberg, Elisabeth, Tatem, Andrew J., Wetter, Erik, Lu, Xin, Power, Daniel, Weidman-Grunewald, Elaine, Ramos, Sergio, Moritz, Simon, Buckee, Caroline O. and Bengtsson, Linus (2018) Population mobility reductions associated with travel restrictions during the Ebola epidemic in Sierra Leone: use of mobile phone data. International Journal of Epidemiology, 47 (5), 1562-1570. (doi:10.1093/ije/dyy095).

Record type: Article

Abstract

Background: Travel restrictions were implemented on an unprecedented scale in 2015 in Sierra Leone to contain and eliminate Ebola virus disease. However, the impact of epidemic travel restrictions on mobility itself remains difficult to measure with traditional methods. New 'big data' approaches using mobile phone data can provide, in near real-time, the type of information needed to guide and evaluate control measures.

Methods: We analysed anonymous mobile phone call detail records (CDRs) from a leading operator in Sierra Leone between 20 March and 1 July in 2015. We used an anomaly detection algorithm to assess changes in travel during a national 'stay at home' lockdown from 27 to 29 March. To measure the magnitude of these changes and to assess effect modification by region and historical Ebola burden, we performed a time series analysis and a crossover analysis.

Results: Routinely collected mobile phone data revealed a dramatic reduction in human mobility during a 3-day lockdown in Sierra Leone. The number of individuals relocating between chiefdoms decreased by 31% within 15 km, by 46% for 15-30 km and by 76% for distances greater than 30 km. This effect was highly heterogeneous in space, with higher impact in regions with higher Ebola incidence. Travel quickly returned to normal patterns after the restrictions were lifted.

Conclusions: The effects of travel restrictions on mobility can be large, targeted and measurable in near real-time. With appropriate anonymization protocols, mobile phone data should play a central role in guiding and monitoring interventions for epidemic containment.

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Accepted/In Press date: 10 May 2018
e-pub ahead of print date: 26 June 2018
Published date: 1 October 2018

Identifiers

Local EPrints ID: 426077
URI: https://eprints.soton.ac.uk/id/eprint/426077
ISSN: 0300-5771
PURE UUID: f8983029-8306-44d9-b031-2aed43971c03
ORCID for Andrew J. Tatem: ORCID iD orcid.org/0000-0002-7270-941X

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Date deposited: 13 Nov 2018 17:30
Last modified: 10 Dec 2019 01:37

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