# COVID-19 Digital Contact Tracing Applications and Techniques: A Review Post
Initial Deployments

Muhammad Shahroz<EMAIL_ADDRESS>Farooq Ahmad
<EMAIL_ADDRESS>Muhammad Shahzad Younis
<EMAIL_ADDRESS>Nadeem Ahmad
<EMAIL_ADDRESS>Maged N. Kamel Boulos<EMAIL_ADDRESS>/<EMAIL_ADDRESS>Ricardo Vinuesa<EMAIL_ADDRESS>Junaid
Qadir<EMAIL_ADDRESS>School of Electrical Engineering and Computer
Science, National University of Sciences and Technology, Islamabad, 44000,
Pakistan.  Cyber Security Cooperative Research Centre, (CSCRC), University of
New South Wales Sydney, New South Wales, Australia.  School of Information
Management, Sun Yat-sen University, East Campus, Guangzhou, 510006, Guangdong,
China.  Department of Mechanical Engineering, KTH Royal Institute of
Technology, Stockholm, Sweden.  Department of Electrical Engineering,
Information Technology University, Lahore, Pakistan.

###### Abstract

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.

###### keywords:

App; contact tracing; COVID-19; data protection; Internet of Things; privacy.

††journal: Journal of LaTeX Templates

##  1 Introduction

The Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) virus and the
associated disease designated as coronavirus disease 2019 (COVID-19), first
reported in China in late 2019, represents the most significant public health
threat in the last 100 years. This disease has spread like wildfire across the
globe. The pandemic response has been mixed. Some countries responded
proactively and effectively, while others botching their responses. One way to
limit the spread of the virus is to ensure strict lockdowns—however, this
comes at a significant economic cost due to industries being shut down and
workers losing jobs, and there is a risk that the spread will start anew once
the lockdowns are lifted [1].

During the early days of the pandemic, human mobility was greatly affected.
People started taking self-isolation measures in their homes. However, it
resulted in the shutting of the transportation industry. Most countries have
focused on developing smart lockdown strategies using various technological
solutions to combat COVID-19 [2, 3]. Overall timely preventive measures and a
mix of high and low technological solutions made it possible for some
countries (such as China, South Korea) to minimize the disease’s spread. These
countries relied on putting international travelers under surveillance and
quarantine. Even low-risk individuals were asked to observe quarantine, and
their physical location was either observed by the government operators or
cell tower location data was used to monitor the quarantine conditions.
Identified cases were kept in special COVID wards for about a fortnight,
depending on health infrastructure availability.

The use of face masks among the masses can drastically reduce the virus’s
spread among healthy individuals [4]. However, the chances of the spread can
still be high. Contact tracing is a technique to identify individuals who have
possibly come in close contact with an infected person while that person was
the carrier of the viral pathogens. Contact tracing is a time-tested technique
employed successfully to control and monitor historical outbreaks of diseases
like HIV, Ebola, and measles. The traditional way of contact tracing is the
manual contact tracing technique, used to identify the close meetups of the
infected person [5]. However, the manual contact tracing technique has two
significant limitations: (1) it requires a sizeable trained workforce to
conduct these manual interviews; and (2) it cannot identify individuals that
are not known to the infected person but have come in close contact (e.g.,
while using public transport or dining in restaurants). Furthermore, manual
contact tracing is a hectic process that requires a centralized, coordinated
effort to identify at-risk close contacts of a COVID positive individual.

Due to the various limitations of manual contact tracing, technologists, in
consultations with the epidemiologists, are now overwhelmingly supplementing
classical contact tracing techniques with digital contact tracing techniques
[6]. Digital contact tracing techniques typically depend on apps installed on
smart mobile phones [7]. These contact tracing apps trace individuals’ meetups
by either using a local Bluetooth connection or the global network of the
Global Positioning System (GPS) for location tracking. In the current crisis,
many IoT-based contact-tracing apps have been deployed [5, 8] or are in the
development phase under the collaborations of government and tech industries
[9, 10, 11]. Countries like Singapore, South Korea, Israel, Italy, Germany,
and China have fully implemented digital contact tracing. Other countries do
not have substantial adoption due to policy issues and concerns about consumer
privacy and legal rights. Big tech companies like Apple and Google [11] have
also joined hands to accelerate the effort on expanding the capabilities of
existing tracing frameworks. Digital contact tracing platforms are thus
emerging as an essential component of global response against the COVID-19.

However, such an approach is not a panacea or a silver bullet. The current
generation of digital contact tracing apps is facing several issues that limit
their effectiveness. This includes low app adoption rates, low mobile phone
penetration, privacy and trust issues, potentially high false-negative rates
(i.e., the app fails to register a close contact with an infected individual
[12]), and the reliance on the tracing apps on Bluetooth for proximity
calculations. In this paper, we present a comprehensive analysis of digital
contact tracing and its supporting IoT framework. Furthermore, we elaborate on
the challenges associated with the 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 discuss open challenges such as scalability, privacy,
adaptability and highlight promising directions for future work.

The rest of the paper is structured as follows. The background of digital
contact tracing, which includes discussion on multiple types of contact-
tracing architecture, review of different existing communication technologies
in contact tracing, and the IoT framework of contact tracing, is presented in
Section 2. The challenges associated with the digital contact tracing
application are discussed in Section 3. The international efforts in digital
contact tracing are discussed in Section 4. The current research gaps in the
literature are identified in Section 5. The emerging communication
technologies that can be used in digital contact tracing are discussed in
Section 6, followed by concluding remarks in Section 7.

##  2 Background

Digital contact tracing is a framework in which smartphones register close
contacts with other smartphones, running the same contact tracing app. In this
section, the architecture of the digital contact tracing framework is
discussed. Furthermore, the communication technologies which are currently
used for digital contact tracing are discussed. Moreover, digital contact
tracing solutions using IoT are also discussed in this section.

###  2.1 Centralized vs. Decentralized Digital Contact Tracing Architecture

Broadly speaking, contact-tracing applications are of two types. In
centralized contact-tracing, mobile phones share their anonymous IDs to a
central server maintaining a centralized database, and the server uses this
database to perform contact-tracing, risk-analysis and alerts notifications to
the users. In decentralized contact-tracing, on the other hand, mobile phones,
instead of a centralized server, perform contact matching and notification by
downloading the contact database from the server. A graphical illustration of
these contact-tracing architectures is presented in Figure 1. In centralized
contact-tracing, the detection is performed in a centralized server. In
contrast, in decentralized contact-tracing, each user smartphone acts as a
local server that shares only the infected individuals’ data to the
centralized server, and then the smartphones will fetch this data periodically
from the server and do contact matching locally. An example of this
decentralized contact-tracing architecture is Apple-Google platform [13]. Note
that in decentralized contact tracing, only the data of an infected person are
shared with the centralized server, and contact matching is performed
locally—a fact that makes the user privacy more effective as compared to the
centralized contact tracing in which data of all individuals are shared with
the centralized server. However, there is still a vigorous debate on the
privacy and security aspects and use of these contact-tracing architectures.

Figure 1: Two types of contact-tracing architecture

###  2.2 Communication Technologies Used in Digital Contact Tracing

To enable technlogy driven social distancing, many communication technologies
are adopted to enhance the effectiveness of the digital contact tracing
solutions [14], e.g., WiFi, Bluetooth, GPS, QR Codes, and Zigbee. A brief
explanation of these communication technologies used in contact-tracing
applications is discussed below, and their coverage ranges and accuracy is
shown in Figure 2.

  1. 1.

WiFi

WiFi is a communication technology which is very effective for contact-tracing
purposes especially in an indoor environment such as multi-story building,
airports, alleys, and parking garages [15]. WiFi provides high accuracy in an
indoor environment compared to GPS or other satellite-based technology, useful
in an indoor environment. In a WiFi system, a wireless transmitter known as
WiFi Access Point (WAP) is required to communicate with its user devices. One
of the potential WiFi technology applications used in contact tracing is
positioning [16, 17]. This is very useful in an indoor environment when a
crowd is buildup in pandemic times, especially in railway platforms and
airports. It is also convenient to use the WiFi hardware facilities due to
their low-cost maintenance and easy deployment.

  2. 2.

Bluetooth

Bluetooth is a wireless communication protocol that is present in almost every
modern mobile phone. There are several versions of Bluetooth protocols.
Bluetooth Low Energy (BLE) is very popular in applications due to its less
energy consumption and low cost. As the contact-tracing apps are required to
run continuously for logging the contacts, BLE low battery consumption is very
well suited. However, BLE has a short-range coverage, mostly indoors. One of
the main advantages of Bluetooth technology is that it can connect a device to
multiple devices without requiring any access point and forming an ad-hoc
called piconet [18].

In Singapore, the government has developed an open-source contact-tracing
protocol called BlueTrace, which is employed in the TraceTogether app [19].
The methodology is very simple; every time the contact-tracing app comes
within the proximity of another app, it will locally save their information
mutually. They may volunteer to share this contact information later with the
health department. Most of the contact-tracing apps utilize Bluetooth for
contact-tracing.

  3. 3.

Global Positioning System

The GPS navigation system uses a network of satellites to locate the exact
position of the GPS-enabled devices. Modern smartphones are GPS enabled, which
can be used for contact tracing as well. The other benefit of GPS is its
global availability. Many countries like
Israel111https://govextra.gov.il/ministry-of-health/hamagen-app/download-en/.
and
Norway222https://helsenorge.no/coronavirus/smittestopplastaccessed2020/05/25.
are using GPS-based contact-tracing mechanism.

GPS technology can also be used to limit the physical contact between people,
e.g., customers can shop online and get the product delivered to their homes
using Unmanned Aerial Vehicles (UAVs) based on GPS technology. Many big retail
and logistic corporations are investing in UAVs to deliver the products to
customer homes like Amazon and DHL. Therefore, the social distancing between
the public can be significantly enhanced using GPS technology.

  4. 4.

QR Codes

Another method of contact tracing is the usage of QR codes where a user will
be manually contributing to the database by taking a picture of visual
computer-aided code at multiple places of business. Mobile phone application
automatically reads hidden geolocation of these QR codes and populates the
database with user details. If a person is tested positive, their contacts at
places they have visited can be identified using contact-tracing based on QR
codes. Such techniques are globally used, with China being a prime example
that has a far higher rate of adoption of QR codes [20].

  5. 5.

Zigbee

Zigbee is also a potential technology that can be used in maintaining social
distancing. Zigbee is a standard-based wireless communication technology used
for low-cost and low-power wireless networks [21]. Zigbee-based devices can
communicate with each other in the range of about 65 feet (20 meters) and can
take unlimited hops. The Zigbee control hub can determine the user’s location,
which can be used for crowd control. Therefore, the Zigbee communication
technology can be used for contact-tracing purposes to avoid the spread of the
virus.

Figure 2: Coverage Area and Accuracy Comparison for Different Sensing
Infrastructures

###  2.3 Digital Contact Tracing with IoT

Internet of Things (IoT) is a system of computing devices that has the ability
to transfer data over a network without requiring human-to-human or human-to-
computer interaction. In the current epidemic, the number of infected cases is
increasing day by day; therefore, it is becoming increasingly hard to rely
only on manual contact tracing.

Digital contact tracing based on IoT can enable a scalable, automated contact-
tracing system that can cope with the ever-increasing workload of contact
tracing. Digital contact tracking is a technique used to aid the contact-
tracing process, which detects the contacts when a person is in the proximity
of an infected person. This can be done either by using GPS location or by
Bluetooth signal. The risk of exposure to the infection depends upon how close
a person comes close to the infected person (say less than 1 meter) and the
duration of this contact. However, proximity tracking does not provide a
complete assessment in tracking contacts with an infected person because of
obstacles between two persons, such as a wall or being enclosed in personal
protective equipment.

Multiple types of contact-tracing frameworks have been established following
regional compatibility, acceptability, privacy, and security laws. Most of
these solutions depend on sensors to either identify the user’s close contacts
to understand the spread of the epidemic or track the location of the users
(tracking solutions). These applications require different permissions or
sensory input to either flag or alert users of imminent virus transmission
threats. Tracking platforms like Google COVID-19 Community Mobility
Reports333https://www.google.com/covid19/mobility/. and Apple COVID-19
Mobility Trends Reports444https://www.apple.com/covid19/mobility., take up
data from millions of users with their consent and aggregate this information
anonymously. This is done to track people and crowds’ movement, to know about
the supposed hotspots, and, most of all, to track the effectiveness of
lockdowns in different places and countries. These contact-tracing apps are
meant for healthy individuals who are keen to know about their susceptibility
to getting infected if they have come across an individual later diagnosed
with COVID-19. With the application of these digital contact tracing apps, the
passenger flow can be control in the passenger waiting areas by forecasting
the transportation data [22].

More aggressive solutions have also been developed to geofence the individuals
in quarantine using dedicated smartphone applications or more straightforward
interaction with the user using a phone call or text message exposing the
geolocation of the user. An IoT hardware-based solution is presented in [23],
in which the information on movement and contacts of objects are captured
using RFID tags. Such implementation is more obligatory than voluntary, with
noncompliance deemed as an offense. Recently a platform named as BubbleBox is
presented in [24], in which the system of integrated IoT devices and a
software platform is used to limit and detect further outbreaks of COVID-19
infections. A BubbleBox device, a wristband, traces contacts under the safe
social distance. With a web-app, the users can pair their identity with their
device, as well as report their symptoms. In this way, they offer the
authorized medical personnel a quick way to understand the infection’s spread,
monitor who needs to be tested and quickly contact patients. Finally, the
collected data, anonymized, can help researchers understand trends about the
spreading of the infection.

Usability is also crucial to increase the number of people who will use the
system and, thus, maximize the coverage of the contact tracing. Finally, as
different apps and systems to aid in contact tracing become popular, such
systems will be effective only if they are interoperable. Therefore, there is
a need to establish a standard for the collected data.

Figure 3: Key Merits of using IoT solution in combating COVID-19

IoT is an innovative technology that can help in tracking all high-risk
patients during the quarantine period. Figure 3 shows the critical merits of
IoT for COVID-19 pandemic. With the successful implementation of this
technology, we expect an improvement in medical and contact tracing staff’s
efficiency with a reduction in their workload.

##  3 Challenges

Since the COVID-19 crisis emerged, everyone is worried about when this
pandemic will stop, and the worldwide lockdown, which caused an unprecedented
economic crisis, will come to an end. Although the use of digital contact
tracing apps has significantly increased, these contact-tracing apps are still
facing issues and challenges apart from the benefits they have delivered. In
this section, we will discuss some of the challenges that impede the
effectiveness of these apps.

###  3.1 User Adaptability

The success of digital contact tracing largely depends on user adaptability.
These apps face a low penetration rate among the masses [25], e.g. Australia’s
COVIDSafe has a 28.6% penetration rate, Singapore’s TraceTogether has a 25%
penetration, India’s Aarogya Setu has 12.05%, Turkey’s Hayat Eve Sığar has 17%
and UK’s NHS COVID-19 App has 28.5%, which are among the highest and many are
below the 10% adoption e.g. Japan’s COCOA has 6.09% and France’s TousAntiCovid
has 3.58%. For a penetration rate of say 25%, when two persons meet at random,
there is only a 6.25% (0.25 $\times$ 0.25) chance that both persons have
installed the app on their mobile. This is the best possible scenario in which
both persons have an app running on their mobile devices. It is a challenge to
achieve high user adaptability, given that the users are skeptical about the
privacy issues surrounding the use of data generated through these apps.

###  3.2 Low Smart Phone Penetration

Another reason for less adaptability of these contract tracing apps is the low
penetration of smartphones [26]. As most of the digital contact tracing apps
are based on smartphones, users with older devices (or smartphones running
out-of-support versions of mobile operating systems) are unable to use these
apps. The smartphone penetration varies with countries, e.g., 24% in India,
81% in the USA, and 95% in S. Korea [27]. Even in a country like the United
States of America, 2 out of 10 individuals do not even use smartphones; many
of those who own such a device may opt not to install the tracing app on their
device. The digital contact tracing is thus only targeting a fraction of the
population that has access to supported devices.

###  3.3 Global Reach

With the presence of automated and manual contact tracing frameworks, it is
critical to gauge the level of effectiveness of both systems. Manual contact
tracing requires reliable government infrastructure and higher funds to run
the whole operation for a long duration. However, automated contact tracing
requires a modern and high-tech infrastructure. The better the technology
infrastructure of a country, the better the digital contact tracing will be.
We have already discussed that smartphone penetration and user adaptability
are risks affecting the success of these apps. Moreover, the elderly and
people from low socioeconomic communities are more vulnerable to being
affected by the outspread. However, these same groups are the one that is most
unlikely to own a smart device. From a global perspective, digital contact
tracing may be suitable for developed countries. However, in developing and
underdeveloped countries, digital contact tracing frameworks may not achieve
their full potential [28].

###  3.4 Privacy and Ethical Issues

The contact-tracing process includes gathering privacy-sensitive information
of individuals. However, privacy-conscious people generally show reluctance to
share their sensitive information, obstructing the whole contact-tracing
procedure. Therefore, privacy-preserving contact-tracing apps are more likely
to be adopted by a large user base. In the literature, privacy-preserving
contact tracing has been proposed even before the COVID-19 pandemic. Proposals
include Efficient Privacy-preserving contact-tracing for Infection Detection
(EPIC) [29] and ENcounter-based Architecture for Contact Tracing (ENACT) [30].
These techniques were developed for privacy-preserving contact tracing and can
be useful in the current scenario as well. Most of the well-known digital
contact tracing apps have some level of privacy built-in. The individuals’
smartphone identities are made anonymous before sharing with other users and
to the centralized database. The database can only use this anonymous identity
for contact matching, risk analysis, etc.

Management of this health crisis of unprecedented magnitude requires desperate
measures, but it cannot compromise civil and privacy rights [31, 32]. This may
result in a restricted contact-tracing framework with lower efficiency. Such
problems with data privacy affect the contact-tracing application of a single
state or a country and questions the inter-operability of multiple contact-
tracing frameworks of different countries with a far higher number of people
crossing borders. Under these circumstances, organizations like the European
Commission have called upon a common approach among all European governments.
A standard policy has been devised which provides multiple recommendations,
i.e., all citizen level data will be encrypted and will be erased once the
pandemic is near its end, use of contact-tracing app should be voluntary
instead of compulsory. Most of all, the application will avoid using location-
based data tracking instead of proximity sensing will be used among users.

All these interventions, which, in a way or another, depending on the
existence of a digitized system, always pose as a threat to ethics, privacy,
and equality. Such subsystems always remain unreachable to some masses which
do not have that level of digital literacy irrespective of the user level of
digital readiness. For example, everyone should be able to access these
technology-based solutions irrespective of what mobile phone they own or which
version of the mobile operating system their devices can support [33].

###  3.5 Technology Limitations and Transparency

Most of the digital contact tracing apps employ the received signal strength
of Bluetooth messages for proximity estimation. This is not a very reliable
mechanism for distance estimation and may result in erroneous measurements. An
error in distance estimation, in turn, can simulate either panic or a false
sense of safety in users. Bluetooth-based proximity sensing with its faults
can alert of an infection risk even if contacts are separated by a wall, or it
can induce a false level of security even in the proximity of an infected
individual who is either not using the application at the moment or if the
proximity-based sensing fails to register the contact.

There are many instances of governments being questioned for the transparency
of their solutions. A significant amount of effort has been spent on the
development of such systems. Still, they are liable to rejection by
individuals if they are not satisfied with the level of privacy and security.
This can affect the trust they have in local government and the healthcare
system to uphold their ethical obligations.

##  4 International Contact Tracing Approaches

The COVID-19 pandemic has taken the world by surprise, mainly due to its
spread rate. Governments are taking every possible measure to protect their
citizens and their economies from this disease’s effects. Many Countries have
done different modeling studies, explicitly evaluating the COVID-19 pandemic
in terms of mathematical modeling of disease transmission rate and spread
pattern [34, 35, 36].

Most of the countries have adopted digital contact solutions to support the
manual tracing processes. These apps vary in the way contact tracing is
performed. Some of the apps use GPS to track the users’ movements, while
others use a more privacy-preserving design based on Bluetooth advertisements
to register close contacts. Some governments have mandated the use of their
apps, while others encourage voluntary adoption. To build trust, many apps
have their source code released for public scrutiny. The list of apps used by
42 different countries with their technology adoption [7] is presented in
Table 1.555See also http://healthcybermap.org/WHO_COVID19/#8. Most of these
international digital contact tracing apps are based on Bluetooth and GPS
technology, while some also use QR.

There is a more significant concern about using such tracing applications
because of the possibility of fine-grained location tracking and access to
private health records. It is essential for an application to be acceptable to
the masses that its working and policies are transparent. While some apps
(mostly from the European countries including Austria, Finland, Denmark,
Norway, Estonia, and United Kingdom) are transparent in terms of their open-
source design and codes, many contact-tracing applications such as those used
by governments of Algeria, Kuwait, and Tunisia have been questioned by Amnesty
International for their lack of transparency. The contact-tracing application
of Qatar is mandatory for citizens and alarmingly requires access to mobile
phone photos. The application of UAE is decentralized on the surface, yet
authorities can fine the individuals avoiding usage or registration of this
application. Furthermore, the contact-tracing application of Iran has been
taken off from Google Play Store for gathering unnecessary data. However,
recent analysis has shown that the effectiveness of these digital solutions
can only be increased once the population participates in the contact-tracing
process effectively [37]. We can learn from Australia and Singapore’s
experience about why their contact-tracing apps are unsuccessful at large and
what steps can be taken to make these successful apps [38]. Google and Apple
also announced their partnership in the ”spirit of collaboration”, and build a
joint effort to enable the use of Bluetooth technology to help governments and
health agencies to reduce the spread of the virus [13].

In Ref. [39], Vinuesa et al. have proposed a socio-technical framework to
evaluate the suitability of digital contact tracing applications. The authors
of this work belong to the Scandinavian countries, Sweden and Denmark. More
specifically, the framework proposed by Vinuesa et al. comprises 19 criteria
that judge the impact of digital contact tracing apps that can be grouped into
three categories (impact on citizens, technology, and governance). The authors
propose that the technology should be centralized and privacy-preserving (an
example architecture is decentralized privacy-preserving proximity tracing
(DP-3T)). The technology should use local and temporary encrypted storage. The
app should be easy to deactivate or remove and should have an open-source
code. In terms of governance, the app should be preferably owned by the state
or a health agency rather than from a private/commercial entity. Open data
governance is preferable to opaque settings. The authors recommend that the
app should be voluntary and that the app should not be made mandatory to
attend certain places. A _sunset clause_ —which specifies an end date when the
collected data will be destroyed unless extended by explicit processes—is
preferable. The framework also recommends concurring with the European Data
Protection Board (EDBP) guidelines that users should have a right to contest
decisions or demand human intervention. Based on this framework, the authors
analyze existing applications and describe how applications such as Stopp
Corona (app from Austria), NHS COVID-19 (initial version proposed by the UK),
and TraceTogether (app from Singapore) all have low scores in governance). The
authors show that the Austrian app has maximum compliance with their suggested
guidelines while NHS COVID-19 had the least compliance of the three considered
apps. Therefore, there is a need for a tool that can measure the effectiveness
of these apps in controlling the spread of the pandemic. Recently a SIR
(Susceptible-Infectious-Recovered) model is presented that can test the impact
of contact tracing apps in different scenarios using demographic, and mobility
data [40].

Countries |  App Name |  Tech |  Voluntary |  Open Source
---|---|---|---|---
Australia |  COVIDSafe |  Bluetooth |  Yes |  Yes
Austria |  Stopp Corona |  Bluetooth, Google/Apple |  Yes |  Yes
Bahrain |  BeAware |  Bluetooth, Location |  No |  No
Belgium |  Belgium’s app |  Bluetooth, Google/Apple |  Yes |  No
Bulgaria |  ViruSafe |  Location |  Yes |  Yes
Canada |  COVID Alert |  Bluetooth, Google/Apple |  Yes |  Yes
China |  Chinese health code system |  Location, Data mining |  No |  No
Cyprus |  CovTracer |  Location,GPS |  Yes |  Yes
Czech |  eRouska |  Bluetooth |  Yes |  Yes
Denmark |  Smittestop |  Bluetooth, Google/Apple |  Yes |  Yes
Estonia |  Estonia’s App |  Bluetooth, DP-3T, Google/Apple |  Yes |  No
Finland |  Ketju |  Bluetooth, DP-3T |  Yes |  Yes
Germany |  Corona-Warn-App |  Bluetooth, Google/Apple |  Yes |  Yes
Ghana |  GH COVID-19 Tracker |  Location |  Yes |  No
Gibraltar |  Beat Covid Gibraltar |  TBD |  No |  No
---|---|---|---|---
Hungary |  VirusRadar |  Bluetooth |  Yes |  No
Iceland |  Rakning C-19 |  Location |  Yes |  Yes
India |  Aarogya Setu |  Bluetooth, Location |  No |  Yes
Indonesia |  PeduliLindungi |  TBD |  No |  No
Iran |  Mask.ir |  Location |  Yes |  No
Ireland |  HSE Covid-19 App |  Bluetooth, Google/Apple |  Yes |  No
Israel |  HaMagen |  Location |  Yes |  Yes
Italy |  Immuni |  Bluetooth, Google/Apple |  Yes |  Yes
Japan |  COCOA |  Google/Apple |  Yes |  No
Kuwait |  Shlonik |  Location |  No |  No
Malaysia |  MyTrace |  Bluetooth, Google/Apple |  Yes |  No
Mexico |  CovidRadar |  Bluetooth |  Yes |  No
New Zealand |  NZ COVID Tracer |  QR codes |  Yes |  No
North Macedonia |  StopKorona |  Bluetooth |  Yes |  Yes
Northern Ireland |  Northern Ireland’s app |  Bluetooth, Google/Apple |  No |  No
Northern Ireland |  Northern Ireland’s app |  Bluetooth, Google/Apple |  Yes |  No
Norway |  Smittestopp |  Bluetooth, Location |  Yes |  No
Philippines |  StaySafe |  Bluetooth |  Yes |  No
Poland |  ProteGO |  Bluetooth |  Yes |  Yes
Qatar |  Ehteraz |  Bluetooth, Location |  No |  No
---|---|---|---|---
Saudi Arabia |  Tawakkalna |  TBD |  No |  No
Singapore |  Trace together |  Bluetooth, Blue Trace |  Yes |  Yes
Switzerland |  Swiss contact-tracing App |  Bluetooth, DP-3T, Google/Apple |  Yes |  No
Thailand |  Mor Chana |  Location, Bluetooth |  Yes |  No
Tunisia |  E7mi |  Bluetooth |  No |  No
Turkey |  Hayat Eve Sığar |  Bluetooth, Location |  No |  No
United Arab Emirates |  TraceCovid |  Bluetooth |  No |  No
United Kingdom |  NHS COVID-19 App |  Bluetooth, Google/Apple |  Yes |  Yes
Table 1: List of countries using different apps and their adopted
technologies.

###  4.1 Suspended, Replaced and Relaunched Apps

During the first wave of the pandemic, many countries launched their apps with
varying degrees of success. Finland’s one million people downloaded Finland’s
app within just 24 hours after the launch, which is around 20% of their
population. This is mainly because of the high penetration rate of smartphones
in the population and prioritized individual privacy using third-party instead
of using the government platform [41]. Similarly, Ireland’s app was downloaded
by 37% of the population just two months after its launch [41]. This success
shows that people value the privacy-preserving attributes of the apps most.

However, apps of some countries are suspended by regulators, some have been
replaced with updated versions since their initial launch, and some have been
relaunched [42]. Iran’s AC19 app was suspended by the Google Play store for
allegedly spying on users, and Japan’s app was suspended two times due to
malfunctioning. Some countries like Norway, Finland, and the UK switched their
apps to the Google/Apple framework for its globally available, well-
established notification system.

These challenges show that the digital contact tracing apps have several gaps
in research for the latest communication technologies, privacy preservation
methodologies, etc., which are discussed in the next sections.

##  5 Current Research Gaps

Digital contact tracing has the potential of playing a significant role in the
current COVID-19 pandemic; however, there are still research gaps to be
addressed. Some of the current research gaps are discussed below.

###  5.1 Urgent Need for Well-Designed Prospective Evaluations of Digital
Contact Tracing Solutions in Real-World Epidemic Settings

There is no published or direct evidence to date (as of December 2020) that
effectively evaluates different digital contact tracing solutions on offer
today in terms of their safety and effectiveness (sensitivity and
specificity), interface accessibility, user acceptance, equitable access
across different age groups and communities, privacy protection and associated
ethical issues when compared with traditional contact tracing in real world
epidemic settings [6]. Despite their promised potential to help identify more
contacts, the actual effectiveness of digital contact tracing solutions
remains unproven [43], and they are unlikely to fit to be used as the sole
method of contact tracing to rely upon during an outbreak. Therefore, there is
an urgent need to conduct robust research to address these aspects and provide
sufficient evidence about how we can best use digital solutions alongside
manual methods for optimal epidemic control.

###  5.2 Scalablity of Existing Contact Tracing Systems

The effectiveness of the current digital contact tracing applications is
directly proportional to the adoption rate of these apps by the masses. This
can be increased through voluntary user adoption by expanding the current IoT
infrastructure and providing strong privacy guarantees. Singapore government
has recently rolled out their COVID tracking tokens targeting population
groups with low smartphone ownership or mastery, especially the elderly who
are not tech-savvy [44]. Although there are still concerns about user data
privacy with the voluntary adoptions of these technologies, scalability can be
increased. Users’ confidence regarding the preservation of their privacy-
sensitive information in current digital contact tracing applications can be
strengthened to enhance the voluntary adoption of these technologies.

###  5.3 Improving the technological impediments

Several technological impediments restrict the use of digital contact tracing
technologies. These include inaccuracy in distance estimations using BLE
signal strength values, interoperability of different apps based on different
architectures, and guarantees regarding privacy and security of data collected
through these apps [8]. Research in these areas will complement the digital
contact tracing platform’s adoption rate to supplement manual contact tracing.

##  6 Emerging Technologies in Digital Contact Tracing

Several emerging technologies have a high potential of being useful in the
context of digital contact tracing. These emerging technologies include
Computer Vision (CV), Artificial Intelligence (AI), Machine Intelligence (MI),
and various kinds of sensors (ultrasound, visible sensors, and thermal) [45].
A brief introduction of these technologies and how they can be used for
contact-tracing purposes is provided in this section.

  1. 1.

Computer Vision, Artificial Intelligence and Machine Learning

Computer Vision (CV) is a technology in which computers are trained to
interpret and understand visual images and videos. With the application of AI
(e.g., deep learning and pattern recognition), CV can detect and classify any
objects using visual data. Using the capabilities of CV based on smart
cameras, we can encourage and enforce social distancing by person re-
identification for positive cases, estimating distances between persons, and
detecting crowds. Sometimes the biases in the data can lead to the
misrepresentation of the CV algorithms. Therefore, the use of CV application
in conjunction with other technologies can provide a reasonable accuracy.

  2. 2.

Ultrasound

Ultrasonic or Ultrasonic Positioning System (UPS) is an indoor environment
communication technology with an accuracy of centimeters [46]. In UPS,
ultrasonic beacons or nodes are used, which periodically broadcast ultrasonic
pulses or Radio Frequency (RF) signals with unique IDs. Using these messages,
the users’ positions can be detected by the position calculation methods such
as trilateration and triangulation [47]. As compared to RF technologies, these
ultrasonic pulses are not affected by electromagnetic interference. However,
it is limited to the indoor environment with short-range coverage. Therefore,
UPS application in contact tracing can be useful in an indoor environment,
especially for high accuracy.

  3. 3.

Visible Sensors

The emergence of Light Emitting Diodes (LEDs) has provided attractive features
of visible lights such as security, privacy, and robustness [48, 49, 50].
Visible Light Communication (VLC) has two components, which include light
transmitters and light receivers. It can provide effective measures in
maintaining social distancing while providing precise location and navigation
in an indoor environment, especially in the epidemic setting, in monitoring
quarantined persons and crowd detection. Due to the low cost and ease of
installation VLC receivers can be used as tags and integrated into mobile
targets such as shopping carts and robots to avoid the build-up of crowds.

  4. 4.

Thermal

Thermal-based positioning is classified into two main categories: Infrared
Positioning (IRP) and Thermal Imaging Camera (TIC). IRPs systems [51, 52] is
considered low-cost, short-range systems (e.g., 10 meters) that can measure
the positions of the targets, while TICs can construct the images of the
objects from heat emission and operate up to kilometers. By combining IRPs and
TICs, social distancing can be monitored in both the indoor and outdoor
environments. Based on the images of the TICs, the position between two
individuals can be calculated, and crowd forming can be avoided.

##  7 Conclusions

There has been wide international adoption of digital contact tracing
applications in the aftermath of the COVID-19 pandemic. Digital contact
tracing is more scalable than manual contact tracing, with the potential of
picking contacts that are otherwise untraceable manually, such as encounters
with strangers in public transport or a coffee shop. Although several research
works have reviewed contract tracing applications and techniques, we present
in this paper a thorough analysis of contact tracing applications and
techniques in the light of initial deployment experiences of these digital
contact tracing technologies and highlight their successes, failures, and
pitfalls. Digital contact tracing applications have faced issues, such as low
mobile phone penetration, poor user adoption, and privacy concerns, to name a
few. In this regard, we discuss how different countries and applications have
made different trade-offs and have therefore experienced different amounts of
success in effectively combating COVID-19. It is noted that while digital
contact tracing apps have their strengths, it is not a panacea; a multi-
pronged COVID-19 response requires digital contact tracing along with
complements such as manual contact tracing, effective coordination and use of
preventive measures such as quarantine isolation, social distancing, hygiene
control, and the use of face masks.

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