Slow virus
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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,[1] subacute sclerosing panencephalitis, the rare result of a measles virus infection,[2] and Paget's disease of bone (osteitis deformans), which may be associated with paramyxoviruses, especially the measles virus and the human respiratory syncytial virus.[3]
Characteristics
Every infectious agent is different, but in general, slow viruses:[4]
- 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,[5] preexisting immunosuppression (as in the cases of JC virus and BK virus),[6] or, in the case of prions, the identity of the agent involved.[7]
Scope
Slow viruses cause a variety of diseases, including cancer.
| Virus | Virus family | Disease | Typical latency | Transmitted by |
|---|---|---|---|---|
| JC virus (Human polyomavirus 2) | Polyomavirus | Progressive multifocal leukoencephalopathy | Years to Life§ | Unknown; possibly contaminated water[6] |
| BK virus | Polyomavirus | BK nephropathy, bladder cancer[8] | Years to life§ | Unknown; possibly respiratory spread/urine; possibly contaminated water[6] |
| Measles virus | Paramyxovirus | Subacute sclerosing panencephalitis | 1–10 years | Respiratory droplets[9] |
| Rubella virus | Togaviridae | Progressive rubella panencephalitis | 10–20 years | Respiratory droplets[10] |
| Rabies virus | Rhabdoviridae | Rabies | 3–12 weeks | Bite of an infected animal[11] |
| Human papillomavirus infection | Papillomaviridae | Cancers of the cervix, oropharynx, vulva, anal, penis, vagina and rectum. | Years | Sexual activity[12] |
- §JC virus & BK virus only cause disease in immunocompromised patients