InfecTracer: Approximate Nearest Neighbors Retrieval of GPS Location Traces to Retrieve Susceptible Cases

Epidemics, such as the present Covid-19 pandemic, usually spread at a rapid rate. Standard models, e.g., the SIR model, have stressed on the importance of finding the susceptible cases to flatten the growth rate of the spread of infection as early as possible. In the present scientific world, location traces in the form of GPS coordinates are logged by mobile device manufacturing and their operating systems developing companies, such as Apple, Samsung, Google etc. However, due to the sensitive nature of this data, it is usually not shared with other organisations, mainly to protect individual privacy. However, in disaster situations, such as epidemics, data in the form of location traces of a community of people can potentially be helpful to proactively locate susceptible people from the community and enforce quarantine on them as early as possible. Since procuring such data for the purpose of restricted use is difficult (time-consuming) due to the sensitive nature of the data, a strong case needs to be made that how could such data be useful in disaster situations. The aim of this article is to to demonstrate a proof-of-the-concept that with the availability of massive amounts of real check-in data, it is feasible to develop a scalable system that is both effective (in terms of identifying the susceptible people) and efficient (in terms of the time taken to do so). We believe that this proof-of-the-concept will encourage sharing (with restricted use) of such sensitive data in order to help mitigate disaster situations. In this article, we describe a software resource to efficiently (consuming a small run-time) locate a set of susceptible persons given a global database of user check-ins and a set of infected people. Specifically, we describe a system, named InfecTracer, that seeks to find out cases of close proximity of a person with another infected person.