Countries across Europe are grappling with how to reopen their economies without putting public health at risk and sparking second spikes of COVID-19 cases.

The most debated and promising instruments to monitor and curb the spread of the virus in the population are contact tracing apps, which have already been successfully used in Asian countries such South Korea to slow the spread of the infection. 

The idea is tantalizing: to help contain infections by harnessing the technological power of the one device billions of people own – a smartphone. Some countries in Europe – France, the UK, and Norway – are already testing their own contact-tracing apps at the national level, while others are still discussing the details of how the system should work.

"As soon as the epidemic started, we thought maybe our software could be used in this type of situation," said Alexandru Pandele, a researcher at Romanian InSpace Engineering. 

Pandele and his team transformed their crowd management app "Agora" into the contact-tracing app "CovTrack," which uses Bluetooth signals to trace interactions and then alerts users if they've been in contact with someone who later tests positive for the coronavirus.

Governments also have access to the information, but Pandele said all data are anonymous. "You are not sharing any data with anybody. You're not sharing your position, you're not sharing your phone's unique Bluetooth address."

CovTrack isn't ready for download yet, but several other contact-tracing apps are already being tested across Europe. In the UK, a National Health Service tracing app is currently being tested on the Isle of Wight, while France's state-backed "StopCOVID" app is expected to enter its testing phase on 11 May. 

But the privacy implications of tracing people's movements are complex and worry lawyers and citizens about what governments will do with individuals' personal data.

From tracing app to surveillance state

The apps could prove vital in preventing a second wave of infection as economies reopen and border controls lift.  But the idea of governments tracking citizens – even in the name of public health – has raised red flags for some who fear it's a slippery slope from good intentions to surveillance state. 

"We saw how CCTV started just to fight petty crime, but now we see the same cameras being repurposed for facial recognition," said Diego Naranjo, head of policy at European Digital Rights. 

Privacy advocates like Naranjo fear the apps could expose personal data such as users' health and location. They're calling for the apps to be voluntary, decentralized and the data encrypted. If these issues aren't addressed, some say the entire project could backfire. 

"If not enough people voluntarily participate, then you know it won't work," said Willem Jonker, CEO of  EIT Digital. "The estimates are that if 60 percent of the population is actively participating, it could be useful."

Brussels is adamant that any tracing apps respect privacy regulations. Parliament adopted a resolution on 17 April which said "mobile location data can only be processed in compliance with the ePrivacy Directive and the GDPR," referring to the EU's strict data protection regulations. Many of the apps under development do steer clear of GPS tracking and right now, all are voluntary.  

But no technology is perfect. Striking the right balance between privacy and public health will be another challenge as Europe slowly reopens after lockdown, one that the European Parliament is discussing in its current plenary session.

The creation of a pan-European system that would allow easier movement across the borders between member states is on hold at the moment, as countries are finding their own solutions.