The real utility of your mobile controlling who you have been close to: this is what bluetooth can do against coronavirus

When Apple and Google announced their alliance to create a Bluetooth-based COVID tracking system that will be integrated in iOS and Android, the more than justified concern about the security and privacy of this type of system has been at the command of the day.

However, there is something that has gone surprisingly unnoticed: its real usefulness in containing the virus and limiting contagion. It should not be forgotten that, in the same week that the announcement was made, Singapore, the country that had become famous for successfully tracking down Bluetooth infections, recognized that its strategy had failed and was forced to impose a generalized quarantine. Are these systems really useful from an epidemiological point of view? We analyze its strengths and weaknesses.

What does "trace with Bluetooth" mean?

This is how the virus moves around the world - Nextstrain.org

Between the outbreak of the outbreak in Lombardy and the first days of the week of March 9, the response of the Spanish Ministry of Health to the increase in cases was always the same: there was no indication of uncontrolled contagion because "more than 90% of the cases are affiliated. " In other words, a clear line could be drawn between nine out of ten cases and an active outbreak of the disease. This (isolating cases, identifying risky contacts, and monitoring them) is the ABC of the containment phase of an infectious disease.

However, there are several ways to do it. The usual way is the one followed in Spain, waiting to identify those infected and trying to reconstruct the steps they had been taking in recent days to quarantine all those who had had risky contacts with those infected. However, several Asian countries decided to do otherwise.

Some countries, such as South Korea, used the GPS of the mobile phones of the infected to ensure that the reconstructions of the routes were as accurate as possible. With that information, they identified how, when and where the infected had moved, and they deployed a whole campaign of public messages (using screens or through a public address system) to warn people who had been “in the hot springs of the city of Yeongju to 17:30 on February 17 or in a private yoga class in Andong after 14:00 on the 18 ”of which they had had risky contacts.

The use of GPS allowed to improve the reconstructions (that until that moment depended on the memory of the patients) and, with this, it allowed to improve the Government's capacity to contain the outbreak. However, GPS was not a panacea. Their data is not only imprecise, but doesn't take into account things like the verticality of buildings. Therefore, shyly in Korea and intensively in Singapore, it was decided to resort to bluetooth.

TraceTogether, the app developed by the Singapore Government Technology Agency, works by keeping locally the identification (and encrypted) codes of the phones that are nearby at all times of the day. In this way, once a case has been identified and with its authorization, the health authorities could notify the people who were nearby to isolate themselves or go to the hospital. The technology that allows you to do this easily is what Apple and Google want to put in every Android and iOS phone in the world.

Can these types of systems be useful?

Kyle glenn

On a theoretical level, yes. In the last decade, as mobile became increasingly ubiquitous, numerous researchers have been working on how to use the information that can be extracted from mobile networks to better understand the dynamics of the epidemic and implement more effective measures that limit contagions. The first conclusion of these years of modeling and simulation is that indeed mobile phones have great potential to fight an epidemic.

Above all, when we talk about an epidemic like the current one in which the disease is highly contagious and the "risk points" number in the thousands. That is why, in the early stages, this type of systems can allow us to preventively isolate everyone who is at risk of being infected (however small it may be). And is that, having information "in real time" of how the virus is moving not only allows us to contain it more efficiently, but also allows us to decide when to move to mitigation scenarios and implement measures of social distancing and quarantine.

What is the problem?

Katayoun Farrahi, Rémi Emonet and Manuel Cebrian

The problem is eminently practical: that we don't know how to do it. First, because it does not seem that the use of systems of this type is going to be obligatory and that means that we will have a very partial vision of what is happening. Singapore only managed to get 12% to install the app and the results speak for themselves.

To give us an idea, with that installation rate, the chances that two people who cross paths have the app on their mobile phones are darn low (1.44% in the US, for example). With these conditions, Bluetooth does not assure us an improvement (or, at least, they are not used by a huge number of people) compared to other traditional methods.

Secondly, due to the technical complexity of determining what a "risk contact" is. At the end of the day, these applications only detect nearby mobiles via bluetooth, but that by itself does not mean anything. Can you effectively differentiate between two people in the same room and two people in different rooms separated by just one brick wall? Can we be sure that only "close" people are detected and that there are no "false contacts"? Well, the truth is that neither of these two things can be guaranteed by the operation of Bluetooth technology.

As we said before, during the early stages, how to prevent the virus from spreading in society. Those "false contagions" can be a risk to take. But, as the number of infected begin to grow and the contagion becomes community, the number of "false suspects" would skyrocket completely. The key issue here is that by the time this system is operational, most of the world will have abandoned contention scenarios where they may have some use.

Third, we must not forget that the mere introduction of tools of this type can change the behavior of citizens and, with it, the course of the epidemics. For better or for worse in the event that people start leaving the phone at home or start using them to confuse the system so that they do not allow us to make an accurate reading of what is really happening on a social level.

Is it reasonable to use them or are doubts justified?

What we have in front of us is a system with serious security and privacy problems and little real utility. Without being able to accurately identify risky contacts and without being able to use it, this system would allow us to improve patient reconstructions at the cost of much revision work. In the early stages of a dangerous pandemic, its use could be studied, but it is far from changing the rules of the game.

The epidemiological studies that we have seen coincide in the "great potential" as well as in the "it is still early". Thus, it does not seem like the best option to dedicate resources to at the moment. However, it would be overly optimistic to think that this global pandemic situation is something exceptional and will not happen again. On the contrary, the WHO has been warning for years that these types of situations are going to become more and more common.

For this reason, it is worth asking if this is not the time to launch this type of initiative to accumulate experience, find solutions to problems and improve systems. Expecting these types of solutions to stop contagion today is not realistic, but it is a perfect time to start developing new technological solutions that avoid them in the future.

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