Joan,
This all depends on how you have the forum set up...
...and on who has rights in the course.
If you use the standard out-of-the-box News Forum then it has its forcesubscribe value set to 1, which means EVERYONE who has the capability 'mod/forum:initialsubscriptions' set to Allow in that
context, will get emailed! ... and that means
all students and all teachers!
You can HIDE the standard news forum, and create your own with other settings.
If you set the answer to the question: Force everyone to be subscribed? to 'No', you can still drop all the names you wish into the subscribers list (and leave off your physicians!)
But why are they getting emails anyway? Are they teacher/instructors on the course, well that forcesubscribe=1 setting will hit them.
Or have they a similar role,
but at a much higher level - say, the system content (whole site) or the category context. The higher up the context level, the more forums might blast them with emails!
So, simply, don't leave forums set to forcesubscribe=1 (that is: the 'Force everyone to be subscribed?' 'Yes, forever' setting).
Then add the subscribers you want to the list.
Hope this gets less grief. regards,
John