  The coronavirus disease 2019 (COVID-19) is a severe global pandemic that has
claimed millions of lives and continues to overwhelm public health systems in
many countries. The spread of COVID-19 pandemic has negatively impacted the
human mobility patterns such as daily transportation-related behavior of the
public. There is a requirement to understand the disease spread patterns and
its routes among neighboring individuals for the timely implementation of
corrective measures at the required placement. To increase the effectiveness of
contact tracing, countries across the globe are leveraging advancements in
mobile technology and Internet of Things (IoT) to aid traditional manual
contact tracing to track individuals who have come in close contact with
identified COVID-19 patients. Even as the first administration of vaccines
begins in 2021, the COVID-19 management strategy will continue to be
multi-pronged for the foreseeable future with digital contact tracing being a
vital component of the response along with the use of preventive measures such
as social distancing and the use of face masks. After some months of deployment
of digital contact tracing technology, deeper insights into the merits of
various approaches and the usability, privacy, and ethical trade-offs involved
are emerging. In this paper, we provide a comprehensive analysis of digital
contact tracing solutions in terms of their methodologies and technologies in
the light of the new data emerging about international experiences of
deployments of digital contact tracing technology. We also provide a discussion
on open challenges such as scalability, privacy, adaptability and highlight
promising directions for future work.
