slow virus slow virus a slow virus is a virus, or a viruslike agent, etiologically associated with a slow virus disease. a slow virus disease is a disease that, after an extended period of latency, follows a slow, progressive course spanning months to years, frequently involves the central nervous system, and in most cases progresses to death. examples of slow virus diseases include hiv/aids, caused by the hiv virus, subacute sclerosing panencephalitis, the rare result of a measles virus infection, and paget's disease of bone (osteitis deformans), which may be associated with paramyxoviruses, especially the measles virus and the human respiratory syncytial virus. characteristics every infectious agent is different, but in general, slow viruses: cause an asymptomatic primary infection have a long incubation period ranging from months to years follow a slow but relentless progressive course leading to death tend to have a genetic predisposition often re-emerge from latency if the host becomes immuno-compromised additionally, the immune system seems to plays a limited role, or no role, in protection from many of these slow viruses. this may be due to the slow replication rates some of these agents exhibit, preexisting immunosuppression (as in the cases of jc virus and bk virus), or, in the case of prions, the identity of the agent involved. scope slow viruses cause a variety of diseases, including cancer. examples of viral agents virusvirus familydiseasetypical latencytransmitted by jc virus (human polyomavirus 2)polyomavirusprogressive multifocal leukoencephalopathyyears to life§unknown; possibly contaminated water bk viruspolyomavirusbk nephropathy, bladder canceryears to life§unknown; possibly respiratory spread/urine; possibly contaminated water measles virusparamyxovirussubacute sclerosing panencephalitis1–10 yearsrespiratory droplets rubella virustogaviridaeprogressive rubella panencephalitis10–20 yearsrespiratory droplets rabies virusrhabdoviridaerabies3–12 weeksbite of an infected animal human papillomavirus infection papillomaviridae cancers of the cervix, oropharynx, vulva, anal, penis, vagina, rectum. years sexual activity §jc virus & bk virus only cause disease in immunocompromised patients kuru- a form of transmissible spongiform encephalopathy was once thought to be due to a slow virus but is now known to be the result of prion disease.