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A slow virus is a virus, or a viruslike agent, etiologically associated with a disease, having a long incubation period of months to years and then a gradual onset of symptoms which progress slowly but irreversibly and terminate in a severe compromised state or, more commonly, death. A slow virus disease is a disease that, after an extended period of latency, follows a slow, progressive course spanning months to years, frequently involving the central nervous system and ultimately leading to death. Examples include the Visna-Maedi virus, in the genus Lentivirus (family Retroviridae), that causes encephalitis and chronic pneumonitis in sheep, and subacute sclerosing panencephalitis which is apparently caused by the measles virus,〔PubMed Health ("Subacute Sclerosing Panencephalitis" ). Retrieved February 10, 2012.〕 as well as Pagets Disease of Bone (Osteitis Deformans) which is associated with paramyxoviridae, especially RSV and Rubeola (Measles). ==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 these slow viruses. This may be in part because the host has acclimated to the virus, or more likely because the host must be immunocompromised in order for many of these slow virus infections to emerge, so the immune system is at a disadvantage from the start. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Slow virus」の詳細全文を読む スポンサード リンク
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