Treating Trauma -- Vicarious Trauma

CNN.com article entitled "Treating Trauma Victims May Cause Its Own Trauma." Psychologists, psychiatrists and other mental health professionals who treat trauma (military or otherwise) are at risk for vicarious trauma -- meaning that they experience an emotional toll after hearing about trauma in their work. How might a mental health professional prevent experiencing vicarious trauma? What should colleagues watch for to prevent emotional distress in their fellow professionals? Do you think this is a risk in non-mental health professionals?