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  • Encounter: having been at or below a distance from another person at the same time t during a period >= p
  • Transmission tracing: mapping how the virus spreads; either through person-to-person transmission, or through environmental transmission
  • Contact: an encounter that really resulted in close interaction between two or more people
  • Cluster: concentration of people in a perimeter, or in a vehicle, either simultaneous or over time
  • Point-of-Interest: a perimeter or building for which we want to monitor the visits
  • Movements: movement of people between two points
  • Path: a calculated route based on GPS measurements
  • Visit: having been at a given point-of-interest, either in open sky or in a building
  • Hotspot: Cluster with infections above a given threshold
  • Exposure: Contact with a possibly infectious person, approximated through an encounter with an infectious subject
  • Spreader: A subject who is the source or possible source of multiple infections. I.c. a person appearing in multiple Exposures and/or appearing in multiple Hotspots.

Expected outcomes

  • Determine ‘encounters’, i.e. having been at or below a distance d from another person at the same time t during a period >= p.
    • Based on: movements paths crossing each other
    • Used for:
      • Giving context to BLE ‘encounters’
      • Determining who has had risk-full encounters
  • Give context to encounters (open space, building, kind of activity, …)
  • Determine ‘visits’, i.e. having been at a given point-of-interest, either in open sky or in a building.
    • Based on:
      • multiple location measurements in a perimeter/geofence
      • interruption of location measurements at a given location (entrance to a building)
    • Used for:
      • identifying possible locations where environmental transmission occurs
      • proxy for non-users in shops, kinder-garten, …
  • Identifying clusters of people (either simultaneous or spread over time) over a given threshold of people per time lapse. These could evolve into Points-of-Interest.
    • ‘Shop’
    • ‘Provincial Domain’
    • ‘Neighborhood party’
    • Not: ‘Garden party’
  • Identifying movements between Clusters.
    • With diagnostic data added
      • Identify exposures
      • Identify hotspots
      • Identify spreaders
    • Aggregated
      • A map of the spread of the infections


  • Personal data (ie data that are not strictly anonymous) can not leave the device, or a personal vault, without the consent of the user.
  • Such consent should only be asked when there is a strong indication that the individual is infectious.

What is sufficient anonymisation of location data?

  • place where home address can be suspected needs to be absent
  • what about work place address?
  • … (TBD) …

Definitions (see model)

  • Transmission Tracing Types
    • Encounters, Visits, Movements and Symptoms
  • Human Contact Tracing (HCT)
  • Primary Care relationship
  • Testing, Isolation, Quarantining Organisation
  • Epidemiologic surveillance
  • Research
  • Autonomous Contact Tracing (ACT)
  • Solution
    • The sum of processes and technologies (components, frameworks, hardware) that make up a …
  • Scenario
    • A combination of solutions
  • System
    • Set of applications, processes and conventions that fulfills a purpose. (example: Human Contact Tracing)
  • Technology
    • Building blocks for building applications. (eg DP3T, Apple/Google framework, …)
  • Accuracy
  • Dependability
  • Speed
  • Interoperability
  • Privacy