[bluecalm]

The takeaway is that it's not always possible to think about all the cases it's worth it to contact the person. At the end of the day it's one phone call or email. Mild inconvenience for potentially life changing chance or information. As long as it's a persona in a position like a doctor o researcher making a call I am happy to waste a minute of my life trusting their judgement.

I don't really like where the EU privacy laws are going. I want "try to be reasonable" option. If they are not I can always tell them to delete my contacts later.

[overscore]

EU data protection laws are reasonable. They allow for public health authorities to take all the steps you're suggesting, and they require companies which hold such information to make them available to those authorities. They do not allow researchers to transfer data to a third party to perform further research. Simple, clear, reasonable, and protective of the basic human rights of the study participants.