The ability of some viruses to remain inactive (latent) for a period of time is exemplified bya. kaposi's sarcoma, which causes a skin cancer in people with aids, but rarely in those not infected by hivb. myasthenia gravis, an autoimmune disease that blocks muscle contraction from time to timec. the virus that causes a form of the common cold, which recurs in patients many time in their livesd. influenza, a particular strain of which returns every 10-20 yearse. herpes simplex viruses (oral or genital) whose reproduction is triggered by physiological or emotional stress in the host