COVID-19 Spatial Contact Tracing

Department: Architecture , Landscape Architecture
Research Centre: Architecture, Urbanism, and the Humanities Initiative
Principal Investigators:
Eric Schuldenfrei, PhD, University of Hong Kong;
Ashley Scott Kelly, University of Hong Kong;
Marc Downie, PhD, University of Chicago; Howard Huang, PhD, IEEE Fellow, Nokia Bell Labs; John Gallacher, PhD, FFPH, University of Oxford.
Funding: Partially supported by a donation from Mimi Brown

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When future epidemic waves of COVID-19 occur, near- instantaneous contact tracing will be essential to lower the transmission growth rate. The recently released Google Apple Contact Tracing (GACT) system only traces device-to-device proximity for users of its app and neglects other crucial spatial- and temporal- aspects of disease transmission. We solve this problem with a simple idea: a Spatial Contract Tracing (SCT) system that tethers static devices (“SCT devices”) to specific spaces.

This idea improves the precision of exposure risk estimates by providing more accurate measures of environment (type of room), distance (between individuals), time (duration and contemporaneity of exposure), and location  (horizontal and vertical coordinates). In the immediate term these metrics enable rapid and comprehensive contact tracing. In the near term they provide an essential natural experiment if transmission models are to be refined and more efficient responses developed.

In the baseline GACT system, mobile devices act as proxies for people, and thus one may speak of devices that are “infected” with COVID-19. GACT detects contact between an infected device and another device when they are within each other’s Bluetooth range. SCT devices mounted on the ceiling of rooms will better detect the presence of all GACT devices. More importantly, these detect contact in five additional situations: app users beyond the GACT detection range; app users occupying the same space at a later time; users holding low-cost Bluetooth beacons; and those reachable by managers of these spaces for users who do not have the app installed or do not own a mobile device.

Alerted contacts could then decide on the relevant level of response to take, which is especially pertinent to those with preexisting health conditions or for contacts who live with or frequently visit individuals at higher risk. Further, because SCT devices run an app following GACT, they inherit the security and privacy features of the GACT system. Lastly, data collected through SCT could be used by epidemiologists to refine the transmission model, thereby enabling more effective contact tracing.

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