Research activities within the Division of Infectious Diseases and Hospital Epidemiology include studies of nosocomial infections, prosthetic joint infections, and Lyme disease. Professor Ruef participates actively in international collaborative studies on nosocomial infections in his function as secretary of the European Study Group for Nosocomial Infections (ESGNI) of  the European Society for Clinical Microbiology and Infectious Diseases (ESCMID).

Educational activities of the Division Chief include participation as teacher within the curriculum of the Faculty of Medicine of the University of Zurich by giving lectures and courses as well as supervising Master thesis projects. Additional educational activities include regular teaching sessions (symposia, other forms of continuous medical education) on the campus of the Hirslanden Medical Center.