The Netherlands-based Public Health Blockchain Consortium (PHBC) has released a blockchain-based system to track and report where people are NOT infected with dangerous viruses. 

Why? To 'certify' them as 'safe zones'. Anyone entering them who may be a carrier of the virus in question can be identified and quarantined as soon as possible. While this might sound a bit like 'big brother,' and I have no doubt there are legal and regulatory issues to consider, this sure sounds to me like an application of this technology worth considering to protect the health and safety of citizens, probably the most important mission of governments everywhere.