Poliomyelitis
| Poliovirus | |
|---|---|
| Scientific classification | |
| Group: | Group IV |
| Order: | Picornavirales |
| Family: | Picornaviridae |
| Genus: | Enterovirus |
| Species: | Enterovirus C |
| Subtype: | Poliovirus |
Description
Poliomyelitis is viral disease caused by an enterovirus known as poliovirus and is well known for its role in causing paralysis, especially in infants. While most infections are asymptomatic, viral particles that gain entrance into the central nervous system can replicate in neurons and destroy cells that govern muscle function resulting in flaccid paralysis.
Epidemics involving the disease, also known as polio, have stuck the human race throughout history. The emergence of polio vaccines in the mid 20th century, however, has given public health organizations the tools needed to eradicate the disease. Worldwide immunization efforts have reduced worldwide cases from the hundreds of thousands to less than a thousand per year. With the Western Hemisphere and Europe declared polio-free in 1994 and 2002 respectively, the virus only remains endemic in Nigeria, Afghanistan and Pakistan. If successfully eradicated, polio will be one of only three diseases eradicated in history—the others being smallpox and rinderpest which were declared eradicated in 1979 and 2011 respectively.
Virology and Taxonomy
Poliovirus is a member of the picornavirus viral family, a taxonomic grouping that includes rhino viruses and hepatisis A virus. Picornaviruses are characterized by their icosahedral capsid structure that lacks a viral envelope and carries the single-strand RNA genome. Enterovirus, the genus that includes poliovirus, represents viruses that can withstand low pH and thus pass through the stomach to infect and replicate within intestinal epithelial cells. This ability allows poliovirus to be highly infectious through the fecal-oral route.
Genome and Structure
The virus’ approximately 7500 nucleotide RNA genome codes for the proteins that form its capsid as well as _______. As the genome is translated within the host cell, the polyprotein is cleaved to release P1, which codes for all the proteins needed to form the capsid. 3CD, a viral protease, cleaves P1 to release VP1, VP3 and myristoyl-VP0 which will form pentamers that will eventually create empty capsids made of 60 copies of each of the aforementioned proteins. Once the RNA genome has been encapsidated, the infectious virion will be formed with the cleavage of VP0 into VP2 and VP4 thus leaving the capsid structure complete with 60 copies each of the four proteins: VP1, VP2, VP3 and VP4.
Serotypes
Three distinct serotypes, PV1, PV2 and PV3, are associated with the paralytic disease with PV1 being associated most frequently with paralytic poliomyelitis.
Pathogenesis
Clinical features
Diagnosis
Treatment
Prevention
Host Immune Response
References
Created by Jake Morgan, student of Tyrrell Conway at the University of Oklahoma.
![[1]](http://commons.wikimedia.org/wiki/File:Polio_EM_PHIL_1875_lores.PNG){kind=link}