As an example US immigration are now sometimes turning away tourists with mental health problems. So in the absence of privacy if you have such problems you can either turn down treatment and suffer or risk being unable to visit or even transit via the US. http://www.telegraph.co.uk/news/worldnews/northamerica/canad...
I remember a similar issue when the italian government decided that it doctors should report treatment of illegal aliens. This just meant that a lot of illegal immigrants didn't want to get cured and it posed a severe risk for public health regarding contagious diseases.
