  We introduce a fundamentally different paradigm for contact tracing: for each
positive case, do not only ask direct contacts to quarantine; instead, tell
everyone how many relationships away the disease just struck (so, "2" is a
close physical contact of a close physical contact). This new approach, which
has already been deployed in a publicly downloadable app, brings a new tool to
bear on pandemic control, powered by network theory. Like a weather satellite
providing early warning of incoming hurricanes, it empowers individuals to see
transmission approaching from far away, and incites behavior change to directly
avoid exposure. This flipped perspective engages natural self-interested
instincts of self-preservation, reducing reliance on altruism, and the
resulting caution reduces pandemic spread in the social vicinity of each
infection. Consequently, our new system solves the behavior coordination
problem which has hampered many other app-based interventions to date. We also
provide a heuristic mathematical analysis that shows how our system already
achieves critical mass from the user perspective at very low adoption
thresholds (likely below 10% in some common types of communities as indicated
empirically in the first practical deployment); after that point, the design of
our system naturally accelerates further adoption, while also alerting even
non-users of the app. This article seeks to lay the theoretical foundation for
our approach, and to open the area for further research along many dimensions.
