A 35-year-old man presents to his physician with a 18Kg weight loss over the preceeding 4 months. The man has not been dieting, but has been having abdominal pain, nausea, and diarrhea. He also had a chronic cough. Sputum studies demonstrate Pneumocystis carinii, and esophagogastroduodenoscopy with biopsy demonstrates Candida and Herpes in the esophagus.The pathogen which causes this patient's underlying disease is a member of which of the following groups of viruses?