Abstract
BackgroundData 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.MethodsThis 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.ResultsThe 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).ConclusionsExposure 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.
Highlights
Epidemiologic surveillance systems conventionally rely on passive reporting from healthcare providers and from active investigation in the field
We focus our attention on call detail records (CDR), which are metadata collected by mobile network operators (MNOs) for billing purposes
We study the introduction of pandemic influenza A/H1N1pdm[09] virus to Iceland in 2009; an isolated island with centralized national health records including influenza‐like illness (ILI) diagnoses, near‐ ubiquitous mobile phone use and one likely port of entry: Keflavik International Airport.[19,20,21,22]
Summary
Epidemiologic surveillance systems conventionally rely on passive reporting from healthcare providers and from active investigation in the field. Mobile phone use is ubiquitous, with even low‐to‐ middle‐income countries having 95% penetration of mobile phones, compared, for example, to only 40% of the population having access to the Internet.[18] Second, CDR provide relatively granular informa‐ tion about where and when their users have travelled, data that can be rapidly anonymized and aggregated by the MNO into an analytic data set for epidemiological analysis. We show that CDR can be used as a proxy for physical proximity, allowing for the analysis of transmission dynamics of H1N1pdm[09] virus within social networks over the course of the epidemic. These investiga‐ tions demonstrate the relevance of CDR to epidemiologic research
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