Flying, phones and flu: Anonymized call records suggest that Keflavik International Airport introduced pandemic H1N1 into Iceland in 2009

• Type of Material: Article
• Authors: Nishant Kishore, Harvard University; Rebecca Mitchell, Emory University; Timothy Lash, Emory University; Carrie Reed, Emory University; Leon Danon, University of Exeter; Guorun Sigmundsdottir, Directorate of Health of Iceland, Reykjavík; Ymir Vigfusson, Emory University
• Language: English
• Date: 2019-11-09
• Publisher: Wiley
• Publication Version: Final Published Version
• Copyright Statement: © 2019 The Authors. Influenza and Other Respiratory Viruses published by John Wiley & Sons Ltd.
• License: Creative Commons Attribution 4.0 International
• Final Published Version (URL): http://dx.doi.org/10.1111/irv.12690
• Title of Journal or Parent Work: Influenza and Other Respiratory Viruses
• Volume: 14
• Issue: 1
• Start Page: 37
• End Page: 45
• Grant/Funding Information: The work is partially supported by Icelandic Centre for Research Award #152620‐051, an Emory University Research Council Award, NSF CAREER Award #1553579, a Leverhulme Early Career Fellowship and a hardware donation from NVIDIA Corporation.; LD gratefully acknowledges the financial support of The Alan Turing Institute under the EPSRC grant EP/N510129/1.
• Keywords: Challenges; Iceland; big data; pandemics; call detail records; Science & Technology; influenza; Virology; Influenza; case-control studies; Infectious Diseases; Social networks; Virus; Life Sciences & Biomedicine; Surveillance; Transmission
• Research Categories: Health Sciences, Nursing; Computer Science; Health Sciences, Immunology; Health Sciences, Public Health; Health Sciences, Epidemiology

Abstract

Background: Data collected by mobile devices can augment surveillance of epidemics in real time. However, methods and evidence for the integration of these data into modern surveillance systems are sparse. We linked call detail records (CDR) with an influenza-like illness (ILI) registry and evaluated the role that Icelandic international travellers played in the introduction and propagation of influenza A/H1N1pdm09 virus in Iceland through the course of the 2009 pandemic. Methods: This nested case-control study compared odds of exposure to Keflavik International Airport among cases and matched controls producing longitudinal two-week matched odds ratios (mORs) from August to December 2009. We further evaluated rates of ILI among 1st- and 2nd-degree phone connections of cases compared to their matched controls. Results: The mOR was elevated in the initial stages of the epidemic from 7 August until 21 August (mOR = 2.53; 95% confidence interval (CI) = 1.35, 4.78). During the two-week period from 17 August through 31 August, we calculated the two-week incidence density ratio of ILI among 1st-degree connections to be 2.96 (95% CI: 1.43, 5.84). Conclusions: Exposure to Keflavik International Airport increased the risk of incident ILI diagnoses during the initial stages of the epidemic. Using these methods for other regions of Iceland, we evaluated the geographic spread of ILI over the course of the epidemic. Our methods were validated through similar evaluation of a domestic airport. The techniques described in this study can be used for hypothesis-driven evaluations of locations and behaviours during an epidemic and their associations with health outcomes.