Optimizing contact tracing policies to intervene in the spread of
COVID-19 in San Francisco, CA
Abstract
COVID-19 success stories from countries using contact tracing as an
intervention tool for the pandemic have motivated US counties to pilot
opt-in contact tracing applications. Contact tracing involves
identifying individuals who came into physical contact with infected
individuals. Recent studies show the effectiveness of contact tracing
scales with the number of people using the applications. We hypothesize
that the effectiveness of contact tracing also depends on the occupation
of the user with a large-scale adoption in certain at risk occupations
being particularly valuable for identifying emerging outbreaks. We build
on an agent-based epidemiological simulator that resolves spatiotemporal
dynamics to model San Francisco, CA, USA. Census, OpenStreetMap,
SafeGraph, and Bureau of Labor Statistics data inform the agent dynamics
and site characteristics in our simulator. We test different agent
occupations that create the contact network, e.g. educators, office
workers, restaurant workers, and grocery workers. We use Bayesian
Optimization to determine transmission rates in San Francisco, which we
validate with transmission rate studies that were recently conducted for
COVID-19 in restaurants, homes and grocery stores. Our sensitivity
analysis of different sights show that the practices that impact the
transmission rate at schools have the greatest impact on the infection
rate in San Francisco. The addition of occupation dynamics into our
simulator increases the spreading rate of the virus, because each
occupation has a different impact on the contact network of a city. We
quantify the positive benefits of contact tracing adopted by at risk
occupation workers on the community and distinguish the specific
benefits on at risk occupation workers. We classify to which degree a
certain occupation is at risk by quantifying the impact (a) the number
of unique contacts and (b) the total number of contacts an individual
has for any given work day on the virus spreading rate. We also attempt
to constrain if, when, and for how long certain sites should be shut
down once exposed to positive cases. Through our research, we are able
to identify the occupations, like educators, that are at greatest risk.
We use common geophysical data analysis techniques to bring a different
set of insights into COVID-19 and policy research.