Acute viral nasopharyngitis pathophysiology: Difference between revisions
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==Overview== | ==Overview== | ||
[[Rhinovirus]] ( | [[Rhinovirus]] (the most common cause of common cold) is usually [[Transmission (medicine)|transmitted]] via [[aerosol]]<nowiki/>s generated by [[coughing]] or [[sneezing]]. Following [[Transmission (medicine)|transmission]], the [[virus]] invades [[epithelial cells]] and causes a release of [[Cytokines|inflammatory cytokines]], leading to the various symptoms of the common cold. | ||
==Pathophysiology== | ==Pathophysiology== | ||
===Virus=== | ===Virus=== | ||
Common colds are most often caused by one of more than 100 [[serovar|serotypes]] of [[rhinovirus]]<nowiki/>es, a type of [[picornavirus]]. Other [[viruses]] | Common colds are most often caused by one of more than 100 [[serovar|serotypes]] of [[rhinovirus]]<nowiki/>es, a type of [[picornavirus]]. Other [[viruses]] that can cause colds are [[coronavirus]], [[human parainfluenza viruses]], [[human respiratory syncytial virus]], [[Adenoviridae|adenoviruses]], [[enterovirus]]es, and [[metapneumovirus]].<ref name="Merck">{{cite web | title = Common Cold (Upper Respiratory Infection) | work = The Merck Manual Online | publisher = [[Merck & Co.]] | date = November 2005 | url = http://www.merck.com/mmpe/sec14/ch188/ch188c.html}}</ref><ref name="CKS">{{cite web | author = CKS | year = 2007 | title = Common Cold (Topic Review) | publisher = Clinical Knowledge Summaries Service | url = http://www.cks.library.nhs.uk/common_cold/view_whole_topic_review}}</ref><ref name="pmid10567986">{{cite journal |vauthors=van Kempen M, Bachert C, Van Cauwenberge P |title=An update on the pathophysiology of rhinovirus upper respiratory tract infections |journal=Rhinology |volume=37 |issue=3 |pages=97–103 |year=1999 |pmid=10567986 |doi= |url=}}</ref> | ||
===Transmission=== | ===Transmission=== | ||
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The common cold virus is [[Transmission (medicine)|transmitted]] between people by one of | The common cold virus is [[Transmission (medicine)|transmitted]] between people by one of two ways: | ||
:# [[aerosol]] form generated by [[coughing]] | :# [[aerosol]] form generated by [[coughing]] and [[sneezing]] | ||
:# [[saliva]] or nasal discharge, either directly or from contaminated surfaces | :# [[saliva]] or nasal discharge, either directly or from contaminated surfaces | ||
* [[Asymptomatic]] patients can transmit the infection, too.<ref name="gsacc">{{cite web | url=http://dh.sa.gov.au/pehs/Youve-got-what/ygw-common-cold.pdf |type = pdf | title=Common Cold | publisher=Department of Health, Government of South Australia | year=2005}}</ref> | * [[Asymptomatic]] patients can transmit the infection, too.<ref name="gsacc">{{cite web | url=http://dh.sa.gov.au/pehs/Youve-got-what/ygw-common-cold.pdf |type = pdf | title=Common Cold | publisher=Department of Health, Government of South Australia | year=2005}}</ref> | ||
* The infectious period (i.e., time during which an infected person can infect others) begins about one day before symptoms begin | * The infectious period (i.e., time during which an infected person can infect others) begins about one day before symptoms begin and continues for the first five days of the illness. | ||
* The [[virus]] enters the [[cell (biology)|cells]] of the [[epithelium]] of the [[nasopharynx]] and rapidly multiplies. | * The [[virus]] enters the [[cell (biology)|cells]] of the [[epithelium]] of the [[nasopharynx]] and rapidly multiplies. | ||
* The [[virus]] enters the body mainly through the [[nose]]. Other entry points include the [[Eye|eyes]] | * The [[virus]] enters the body mainly through the [[nose]]. Other entry points include the [[Eye|eyes]] through drainage of [[tears]] from the [[lacrimal ducts]] into the [[nasopharynx]]. | ||
<br clear="left" /> | <br clear="left" /> | ||
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==Pathogenesis== | ==Pathogenesis== | ||
* [[Viruses]] undergo frequent changes in their [[Antigenic|antigenic coat]]. This helps them | * [[Viruses]] undergo frequent changes in their [[Antigenic|antigenic coat]]. This helps them evade the [[immune system]] and enables them to cause recurrent infections. | ||
** [[Rhinovirus]] binds to [[ICAM-1]] receptors on [[epithelial cells]] | ** [[Rhinovirus]] binds to [[ICAM-1]] receptors on [[epithelial cells]] and makes them release [[Cytokine|inflammatory cytokines]], but does not cause damage to them. | ||
** [[Respiratory syncytial virus|Respiratory syncytial virus (RSV)]] does not cause any release of [[cytokines]]. Instead, it replicates in the nose and [[pharynx]]. In many occasions, it can spread to the [[lower respiratory tract]].<ref name="pmid27251607">{{cite journal |vauthors=Blaas D, Fuchs R |title=Mechanism of human rhinovirus infections |journal=Mol Cell Pediatr |volume=3 |issue=1 |pages=21 |year=2016 |pmid=27251607 |pmc=4889530 |doi=10.1186/s40348-016-0049-3 |url=}}</ref> | ** [[Respiratory syncytial virus|Respiratory syncytial virus (RSV)]] does not cause any release of [[cytokines]]. Instead, it replicates in the nose and [[pharynx]]. In many occasions, it can spread to the [[lower respiratory tract]].<ref name="pmid27251607">{{cite journal |vauthors=Blaas D, Fuchs R |title=Mechanism of human rhinovirus infections |journal=Mol Cell Pediatr |volume=3 |issue=1 |pages=21 |year=2016 |pmid=27251607 |pmc=4889530 |doi=10.1186/s40348-016-0049-3 |url=}}</ref> | ||
** [[Human parainfluenza virus]] causes [[inflammation]] of the respiratory tract | ** [[Human parainfluenza virus]] causes [[inflammation]] of the respiratory tract, so [[Parainfluenza virus|parainfluenza]] infection is much more severe than other [[viruses]]. | ||
* The body | * The body fights the offending [[virus]]es using both [[humoral immunity]] (i.e. [[IgA]] in the [[epithelium]]), and [[Cell-mediated immunity|cell mediated immunity]] (i.e. different [[inflammatory cells]] in the [[adenoids]] and [[tonsils]]).<ref name="pmid10567986">{{cite journal |vauthors=van Kempen M, Bachert C, Van Cauwenberge P |title=An update on the pathophysiology of rhinovirus upper respiratory tract infections |journal=Rhinology |volume=37 |issue=3 |pages=97–103 |year=1999 |pmid=10567986 |doi= |url=}}</ref> | ||
* [[Normal flora]] inhabitants in the [[nasopharynx]] also play an important role in eliminating the infection. | * [[Normal flora]] inhabitants in the [[nasopharynx]] also play an important role in eliminating the infection. | ||
==References== | ==References== | ||
Revision as of 14:54, 9 August 2017
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1];Associate Editor(s)-in-Chief: Ahmed Younes M.B.B.CH [2]
Overview
Rhinovirus (the most common cause of common cold) is usually transmitted via aerosols generated by coughing or sneezing. Following transmission, the virus invades epithelial cells and causes a release of inflammatory cytokines, leading to the various symptoms of the common cold.
Pathophysiology
Virus
Common colds are most often caused by one of more than 100 serotypes of rhinoviruses, a type of picornavirus. Other viruses that can cause colds are coronavirus, human parainfluenza viruses, human respiratory syncytial virus, adenoviruses, enteroviruses, and metapneumovirus.[1][2][3]
Transmission
 |
The common cold virus is transmitted between people by one of two ways:
- Asymptomatic patients can transmit the infection, too.[4]
- The infectious period (i.e., time during which an infected person can infect others) begins about one day before symptoms begin and continues for the first five days of the illness.
- The virus enters the cells of the epithelium of the nasopharynx and rapidly multiplies.
- The virus enters the body mainly through the nose. Other entry points include the eyes through drainage of tears from the lacrimal ducts into the nasopharynx.
{{#ev:youtube|GoRhRJXp0j8}}
Pathogenesis
- Viruses undergo frequent changes in their antigenic coat. This helps them evade the immune system and enables them to cause recurrent infections.
- Rhinovirus binds to ICAM-1 receptors on epithelial cells and makes them release inflammatory cytokines, but does not cause damage to them.
- Respiratory syncytial virus (RSV) does not cause any release of cytokines. Instead, it replicates in the nose and pharynx. In many occasions, it can spread to the lower respiratory tract.[5]
- Human parainfluenza virus causes inflammation of the respiratory tract, so parainfluenza infection is much more severe than other viruses.
- The body fights the offending viruses using both humoral immunity (i.e. IgA in the epithelium), and cell mediated immunity (i.e. different inflammatory cells in the adenoids and tonsils).[3]
- Normal flora inhabitants in the nasopharynx also play an important role in eliminating the infection.
References
- ↑ "Common Cold (Upper Respiratory Infection)". The Merck Manual Online. Merck & Co. November 2005.
- ↑ CKS (2007). "Common Cold (Topic Review)". Clinical Knowledge Summaries Service.
- ↑ 3.0 3.1 van Kempen M, Bachert C, Van Cauwenberge P (1999). "An update on the pathophysiology of rhinovirus upper respiratory tract infections". Rhinology. 37 (3): 97–103. PMID 10567986.
- ↑ "Common Cold" (PDF) (pdf). Department of Health, Government of South Australia. 2005.
- ↑ Blaas D, Fuchs R (2016). "Mechanism of human rhinovirus infections". Mol Cell Pediatr. 3 (1): 21. doi:10.1186/s40348-016-0049-3. PMC 4889530. PMID 27251607.