Acute viral nasopharyngitis pathophysiology
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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
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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.
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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.