More importantly, what happens if there is a short somewhere and the USB port becomes connected to mains voltage ? Computers are not medical devices, and I'd sa

More importantly, what happens if there is a short somewhere and the USB port becomes connected to mains voltage ? Computers are not medical devices, and I'd say it is fairly common to feel a small tingle when touching ports so isolation is not that great. The actual medical device should use an isolation transformer or be powered by batteries.