The EU's coronavirus contact tracing guidelines

Coronavirus contact tracing apps used in the EU should protect privacy and be compatible enough with one another to track the spread of the virus across borders, the European Commission wrote to its members on Thursday.

Why it matters: Contact tracing — or tracking down those who have interacted with a virus patient and advising them to self-isolate — is seen as a key step, along with widespread testing, in order to mitigate the spread of COVID-19.

Where it stands: In countries like France, Norway and Poland, Bluetooth is the primary strategy for contact tracing apps, the EU reports. The organization says that contact tracing should not rely on location data.

• The Czech Republic is piloting using users' locations to build maps of where they have spent significant time within the last five days. The tech is operating in three regions, per the EU.
• In the U.S., Apple and Google have proposed technology that notifies users if they've come into contact with someone with the virus, without sharing location data with the government.
• MIT researchers are building a system that matches Bluetooth signals emitted from an infected individual's smartphone over 14 days to other phones, to find who they've come into contact with.

What they're saying: “Mobile apps can warn us of infection risks and support health authorities with contact tracing, which is essential to break transmission chains. We need to be diligent, creative, and flexible in our approaches to opening up our societies again," Stella Kyriakides, the EU health commissioner, said in a Thursday press release.

• The ACLU stressed in a white paper on Thursday that contact tracing apps should be voluntary and preserve users' privacy. The group pointed to Apple and Google's plan as an example of a privacy-friendly approach.

Background: Large-scale testing, contact tracing, a health system that can withstand new patient surges, and a sustained pattern of lowered infections are all necessary for countries to relax quarantines, the European Commission advised on Wednesday.

• The ability of competing apps to work together "would allow for a more effective warning of people concerned and a more efficient public health policy follow-up," the Commission said on Wednesday.

Go deeper: Contact tracing is the latest coronavirus red flag