Help Net Security’s article Crypto ransomware hits German hospitals, based on this article from DW, also includes links to its story about the attack on the Hollywood Presbyterian Medical Center, and another story about a New Zealand hospital hit with Locky. [Added later: Commentary by John Leyden for The Register here. And I’ve just caught up with an article from My News LA about an apparent attack on the Los Angeles Department of Health.]
As far as I can make out there is no firm indication of links between all these attacks, or that hospitals are being specifically targeted by specific malware, but the clustering is worrying. If nothing else, it is clear that hospitals, like any other organization, survive such attacks better if they have suitably-protected backups and other well-administered security precautions in place.