Slow virus
Encyclopedia
A slow virus is a virus
, or a viruslike agent, etiologically associated with a disease
having a long incubation period
of months to years with a gradual onset frequently terminating in severe illness and/or death.
A slow virus disease is a disease that follows a slow, progressive course spanning months to years, frequently involving the central nervous system
and ultimately leading to death; examples are visna and maedi of sheep, caused by viruses of the genus
Lentivirus
(family Retroviridae), and subacute sclerosing panencephalitis
, apparently caused by the measles virus.
Transmissible spongiform encephalopathies
(TSEs), including Creutzfeldt–Jakob disease of humans, scrapie
of sheep, and bovine spongiform encephalopathy
(BSE) of cattle may also be classified under slow virus disease but are now considered to be prion
diseases. A minority of researchers believe, however, that prion diseases are caused by an as-yet unidentified slow virus.
Characteristics of slow virus diseases are:
Virus
A virus is a small infectious agent that can replicate only inside the living cells of organisms. Viruses infect all types of organisms, from animals and plants to bacteria and archaea...
, or a viruslike agent, etiologically associated with a disease
Disease
A disease is an abnormal condition affecting the body of an organism. It is often construed to be a medical condition associated with specific symptoms and signs. It may be caused by external factors, such as infectious disease, or it may be caused by internal dysfunctions, such as autoimmune...
having a long incubation period
Incubation period
Incubation period is the time elapsed between exposure to a pathogenic organism, a chemical or radiation, and when symptoms and signs are first apparent...
of months to years with a gradual onset frequently terminating in severe illness and/or death.
A slow virus disease is a disease that follows a slow, progressive course spanning months to years, frequently involving the central nervous system
Central nervous system
The central nervous system is the part of the nervous system that integrates the information that it receives from, and coordinates the activity of, all parts of the bodies of bilaterian animals—that is, all multicellular animals except sponges and radially symmetric animals such as jellyfish...
and ultimately leading to death; examples are visna and maedi of sheep, caused by viruses of the genus
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
Lentivirus
Lentivirus
Lentivirus is a genus of slow viruses of the Retroviridae family, characterized by a long incubation period...
(family Retroviridae), and subacute sclerosing panencephalitis
Subacute sclerosing panencephalitis
Subacute sclerosing panencephalitis is a rare chronic, progressive encephalitis that affects primarily children and young adults, caused by a persistent infection of immune resistant measles virus . No cure for SSPE exists, but the condition can be managed by medication if treatment is started at...
, apparently caused by the measles virus.
Transmissible spongiform encephalopathies
Transmissible spongiform encephalopathy
Transmissible spongiform encephalopathies , also known as prion diseases, are a group of progressive conditions that affect the brain and nervous system of many animals, including humans. According to the most widespread hypothesis they are transmitted by prions, though some other data suggest an...
(TSEs), including Creutzfeldt–Jakob disease of humans, scrapie
Scrapie
Scrapie is a fatal, degenerative disease that affects the nervous systems of sheep and goats. It is one of several transmissible spongiform encephalopathies , which are related to bovine spongiform encephalopathy and chronic wasting disease of deer. Like other spongiform encephalopathies, scrapie...
of sheep, and bovine spongiform encephalopathy
Bovine spongiform encephalopathy
Bovine spongiform encephalopathy , commonly known as mad-cow disease, is a fatal neurodegenerative disease in cattle that causes a spongy degeneration in the brain and spinal cord. BSE has a long incubation period, about 30 months to 8 years, usually affecting adult cattle at a peak age onset of...
(BSE) of cattle may also be classified under slow virus disease but are now considered to be prion
Prion
A prion is an infectious agent composed of protein in a misfolded form. This is in contrast to all other known infectious agents which must contain nucleic acids . The word prion, coined in 1982 by Stanley B. Prusiner, is a portmanteau derived from the words protein and infection...
diseases. A minority of researchers believe, however, that prion diseases are caused by an as-yet unidentified slow virus.
Characteristics of slow virus diseases are:
- They have long incubation periods ranging from months to years.
- They have slow but relentless progressive courses terminating fatally.
- They have a genetic pre-disposition.
- The immune system does not seem to play a role in its protection.