Pain is the best teacher
Teaching users to be careful is a never-ending task. You can tell a person a hundred times to back up his data, one day he will still get it wiped and moan that he's lost everything. That, most of the time, is the day people become sensitive to the argument.
Here it is worse. Hospital staff are harassed all day, doing five things at a time and some of those can entail risk for life if done wrong. Asking them to beware of their tools in addition is really hard to do.
The scum that launch these mails should be found and shot for putting lives at risk.