COVID19 — Making sense of contact tracing apps

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Some countries are still discussing contact tracing apps, other countries have already launched them, or at least the pilots for it. How do these apps work and do they make any sense at all? Simple questions that will lead to not so simple answers.

Let us start with the purpose of coronavirus contact tracing apps. The goal of these apps is to track mobile phones and devices which were in Bluetooth proximity reach of the participants and respond when any of these contacts are (suspected to be) infected with COVID19.

OK, the first thing we must narrow down is how the contact tracing works. These apps track mobile phones and devices which were in Bluetooth reach and use the same app or platform. This means that these apps do not track contact with devices which either do not use the same app or platform, or do not have their Bluetooth activated and discoverable.

The next thing we need to keep in mind is that most mobile devices use Class 2 Bluetooth transmitters with a range of max. 10 meters / 33 ft., and some even Class 3 transmitters with a range of max 2 meters / 6 ft. Both ranges are reduced significantly when there are a lot of signals in the same area. Even when most smart phones and tablets use a class 2 transmitter, the effective signal range can be less than 3 meters / 10 feet in a busy are like e.g. on public transportation or even in an office with a lot of equipment.

So, the technical restrictions are clear. Contacts are only traced with devices which have the same app or platform, their Bluetooth activated and discoverable, and are within reach which varies based on the circumstances. This brings us to the practical restrictions.

  • People who do not install the apps on their devices can be infected with COVID19 but are not tracked by the apps on devices of others.
  • People who are infected with COVID19 can not be aware of that because they are asymptomatic but as the data provided by the WHO confirms, they can still infect others.
  • People who are infected with COVID19 and are not aware of that during the incubation period of up to 10 days, can infect others.

These COVID19 contact tracing apps depend on the technical aspects and on the fact that people who are aware of being infected or suspected of being infected actually report it or register it, directly or indirectly within the app or platform. This only makes sense when a very high share of people uses the app, and a very high share of people get tested for COVID19.

Why is testing for COVID19 so important in combination with contact tracing apps? As mentioned, it is already confirmed that asymptomatic infections can still cause new infections. Without very aggressive testing, these cases are not registered. Also, during the incubation period of COVID19 the infection can spread to others. None of this will show up in the contact tracing apps until it is too late, or even not at all.

The spread of usage of the app is just as important as aggressive testing for COVID19 infections. Only when a very high share of the population, at least 60%, actively use the app, and each and every suspected infection is aggressively tested and reported, contact tracing could help slow the spread and prevent undetected infections. Until the share of usage is well above 60% and the active testing has reached levels like demonstrated by for example Germany, the contact tracing apps do not make much sense.

There is however a hidden risk when the share of active usage and the share of testing are too low. A false sense of safety and security. Especially with those apps that claim to be able to warn the user when a confirmed COVID19 infection is within reach. Although the restrictions are clear, the users will feel safe when the apps give no alert, and that is not what the intention is. Fighting COVID19 is about preventing infecting others. Encouraging a false sense of safety is about the last thing we need!

The United Kingdom and the NHS launched a pilot for a COVID19 contact tracing app which sums up how it should not be done. Failure by design and a very low likelihood of the massive usage needed to have a positive impact on reducing (undetected) the spread of the coronavirus. Combine that with the low COVID19 testing capacity which still does not reach the already relatively low testing capacity goal the British Government has set itself, and the outcome is clear: an empty shell with a high sense of false safety!

Learn what Cyber Security and Privacy expert Bill Mew has to say about the NHS app:

Read more about the failing COVID19 policy in the UK:

Written by

Dad, consultant, coach, speaker, author. Mainly Cyber Security, leadership, responsible tech and organizational change.

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