If diagnosed with mono, does one need to stay home from work at office- type job, and/or from school? If so, for how long? (to avoid transmission)

No. People who get infectious mononucleosis can shed virus and infect other people for months to years after becoming ill, but mono is not a super contagious illness. You can go back to work or school when your fatigue is better and your energy is up to it. The main concern is for sports. The spleen can get quite enlarged in mono and can even rupture, so get checked out before going back to sports.