Public health professionals recognize that no single term satisfactorily characterizes such diverse groups of individuals as the “marginalized,” the “under-served” or the “at-risk” population. In flu planning and response, elements of the following definition are in use in many health departments across Canada to identify the people requiring specific flu prevention and care services tailored to their unique needs: groups whose needs are not fully addressed by traditional services or who cannot comfortably or safely access and use the standard resources offered in emergency preparedness, response and recovery.