Can mobile phone traces help shed light on the spread of Zika in Colombia?

Daniela Perrotta at UN Global Pulse: “Nowadays, thanks to the continuous growth of the transport infrastructures, millions of people travel every day around the world, resulting in more opportunities for infectious diseases to spread on a large scale faster than ever before. Already at the beginning of the last century, between 1918 and 1920, due to the special circumstances that were created during World War I, such as overcrowded camps and hospitals, and soldiers piled in trenches or in transit every day, the Spanish Flu killed between 20 and 100 million people, more than the war itself, resulting perhaps in the most lethal pandemic in the history of humankind.

The question that then arises naturally is the following: what if an equally virulent and deadly virus would hit today’s highly-connected world where nearly any point can be easily reached in less than a day’s journey?…

To overcome these limitations, more and more sources of data and innovative techniques are used to detect people’s physical movements over time, such as the digital traces generated by human activities on the Internet (e.g. Twitter, Flickr, Foursquare) or the footprints left by mobile phone users’ activity. In particular, cellular networks implicitly bring a large ensemble of details on human activity, incredibly helpful for capturing mobility patterns and providing a high-level picture of human mobility.

In this context, the Computational Epidemiology Lab at the ISI Foundation in Turin (Italy), in collaboration with UN Global Pulse, an innovation initiative of the United Nations, and Telefonica Research in Madrid (Spain), is currently investigating the human mobility patterns relevant to the epidemic spread of Zika at a local level, in Colombia, mainly focusing on the potential benefits of harnessing mobile phone data as a proxy for human movements. Specifically, mobile phone data are defined as the information elements contained in call detail records (CDRs) created by telecom operators for billing purposes and summarizing mobile subscribers’ activity, i.e. phone calls, text messages and data connections. Such “digital traces” are continuously collected by telecom providers and thus represent a relatively low-cost and endless source for identifying human movements at an unprecedented scale.

In this study, more than two billion encrypted and anonymized calls made by around seven million mobile phone users in Colombia have been used to identify population movements across the country. To assess the value of such human mobility derived from CDRs, the data is evaluated against more traditional methods: census data, that are considered as a reference since they ideally represent the entire population of the country and its mobility features, and mobility models, i.e. the gravity model and the radiation model, that are the most commonly used today. In particular, the gravity model assumes that the number of trips increases with population size and decreases with distances, whereas the radiation model assumes that the mobility depends on population density….(More)”.