Respiratory tract infection

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Respiratory tract infection
Illu conducting passages.svg
Conducting passages
SpecialtyInfectious disease

A respiratory tract infection (RTI) is any of a number of infectious diseases involving the respiratory tract. An infection of this type is normally further classified as an upper respiratory tract infection (URI or URTI) or a lower respiratory tract infection (LRI or LRTI). Lower respiratory infections, such as pneumonia, tend to be far more serious conditions than upper respiratory infections, such as the common cold.


Upper respiratory tract infection[edit]

The upper respiratory tract is generally considered to be the airway above the glottis or vocal cords, sometimes it is taken as the tract above the cricoid cartilage. This part of the tract includes the nose, sinuses, pharynx, and larynx.

Typical infections of the upper respiratory tract include tonsillitis, pharyngitis, laryngitis, sinusitis, otitis media, certain types of influenza, and the common cold.[1] Symptoms of URIs can include cough, sore throat, runny nose, nasal congestion, headache, low grade fever, facial pressure and sneezing.

Lower respiratory tract infection[edit]

The lower respiratory tract consists of the trachea (wind pipe), bronchial tubes, the bronchioles, and the lungs.

Lower respiratory tract infections are generally more serious than upper respiratory infections. LRIs are the leading cause of death among all infectious diseases.[2] The two most common LRIs are bronchitis and pneumonia.[3] Influenza affects both the upper and lower respiratory tracts, but more dangerous strains such as the highly pernicious H5N1 tend to bind to receptors deep in the lungs.[4]


Deaths from respiratory infections per million persons in 2012

A 2014 systematic review of clinical trials does not support using routine rapid viral testing to decrease antibiotic use for children in emergency departments.[5] It is unclear if rapid viral testing in the emergency department for children with acute febrile respiratory infections reduces the rates of antibiotic use, blood testing, or urine testing.[5] The relative risk reduction of chest x-ray utilization in children screened with rapid viral testing is 77% compared with controls.[5] In 2013 researchers developed a breath tester that can promptly diagnose lung infections.[6][7]


Despite superior filtration capability of N95 filtering facepiece respirators measured in vitro, insufficient clinical evidence has been published to determine whether normal surgical masks and N95 filtering facepiece respirators are equivalent with respect to preventing respiratory infections in healthcare workers.[8]

Adults in intensive care units (ICU) have a higher risk of acquiring an RTI.[9] A combination of topical and systematic antibiotics taken prophylactically can prevent infection and improve overall mortality for adults in ICU.[9] There is no sufficient evidence to recommend that antibiotics be used to prevent complications from an RTI of unknown cause in children under the age of 5 years old.[10] High-quality clinical research in the form of randomized controlled trials assessed the effectiveness of Vitamin D, [11] other review of poorer quality RCTs addressed the effectiveness of immunostimulants for preventing respiratory tract infections,[12] but exercise effectiveness is not yet clear.[13]

Because viruses that cause RTI are more transmissible at very high or low relative humidity, ideal humidity for indoor spaces is between 40–60%. Relative humidity in this range can help the lessen risk of aerosol transmission.[14]


Respiratory infections often have strong seasonal patterns, with temperate climates more affected during the winter. Several factors explain winter peaks in respiratory infections, including changes in environmental conditions and changes in human behaviors. Viruses that cause respiratory infections are affected by environmental conditions like relative humidity and temperature. Temperate climate winters have lower relative humidity, which is known to increase transmission of influenza.[14]

Of the viruses that cause respiratory infections in humans, most have seasonal variation in prevalence. Influenza, Human orthopneumovirus (RSV), and human coronaviruses are more prevalent in the winter. Human bocavirus and Human metapneumovirus occur year-round, rhinoviruses (which cause the common cold) occur mostly in the spring and fall, and human parainfluenza viruses have variable peaks depending on the specific strain. Enteroviruses, with the exception of rhinoviruses, tend to peak in the summer.[14]


  1. ^ Eccles MP, Grimshaw JM, Johnston M, et al. (2007). "Applying psychological theories to evidence-based clinical practice: identifying factors predictive of managing upper respiratory tract infections without antibiotics". Implement Sci. 2: 26. doi:10.1186/1748-5908-2-26. PMC 2042498. PMID 17683558.
  2. ^ Robert Beaglehole...; et al. (2004). The World Health Report 2004 - Changing History (PDF). World Health Organization. pp. 120–4. ISBN 92-4-156265-X.
  3. ^ Antibiotic Expert Group. Therapeutic guidelines: Antibiotic. 13th ed. North Melbourne: Therapeutic Guidelines; 2006.
  4. ^ van Riel D, Munster VJ, de Wit E, et al. (April 2006). "H5N1 Virus Attachment to Lower Respiratory Tract". Science. 312 (5772): 399. doi:10.1126/science.1125548. PMID 16556800.
  5. ^ a b c Doan, Quynh; Enarson, Paul; Kissoon, Niranjan; Klassen, Terry P.; Johnson, David W. (2014-09-15). "Rapid viral diagnosis for acute febrile respiratory illness in children in the Emergency Department". The Cochrane Database of Systematic Reviews (9): CD006452. doi:10.1002/14651858.CD006452.pub4. ISSN 1469-493X. PMC 6718218. PMID 25222468.
  6. ^ "Breath Test Could Sniff Out Infections in Minutes". Scientific American. 11 January 2013. Retrieved 5 February 2013.
  7. ^ Zhu, Jiangjiang; Bean, Heather D; Wargo, Matthew J; Leclair, Laurie W; Hill, Jane E (2013). "Detecting bacterial lung infections:in vivo evaluation of in vitro volatile fingerprints". Journal of Breath Research. 7 (1): 016003. Bibcode:2013JBR.....7a6003Z. doi:10.1088/1752-7155/7/1/016003. PMC 4114336. PMID 23307645.
  8. ^ Smith, JD; MacDougall, CC; Johnstone, J; Copes, RA; Schwartz, B; Garber, GE (17 May 2016). "Effectiveness of N95 respirators versus surgical masks in protecting health care workers from acute respiratory infection: a systematic review and meta-analysis". CMAJ : Canadian Medical Association Journal. 188 (8): 567–74. doi:10.1503/cmaj.150835. PMC 4868605. PMID 26952529.
  9. ^ a b D'Amico, Roberto; Pifferi, Silvia; Torri, Valter; Brazzi, Luca; Parmelli, Elena; Liberati, Alessandro (7 October 2009). "Antibiotic prophylaxis to reduce respiratory tract infections and mortality in adults receiving intensive care". Cochrane Database of Systematic Reviews (4): CD000022. doi:10.1002/14651858.CD000022.pub3. hdl:11380/864494. PMC 7061255. PMID 19821262.
  10. ^ Alves Galvão, Márcia G; Rocha Crispino Santos, Marilene Augusta; Alves da Cunha, Antonio JL (29 February 2016). "Antibiotics for preventing suppurative complications from undifferentiated acute respiratory infections in children under five years of age". Cochrane Database of Systematic Reviews. 2: CD007880. doi:10.1002/14651858.CD007880.pub3. PMID 26923064.
  11. ^ Martineau, Adrian R; Jolliffe, David A; Hooper, Richar L (15 February 2017). "Vitamin D supplementation to prevent acute respiratory tract infections: systematic review and meta-analysis of individual participant data". BMJ. 356: i6583. doi:10.1136/bmj.i6583. PMC 5310969. PMID 28202713.
  12. ^ Del-Rio-Navarro, Blanca Estela; Espinosa-Rosales, Francisco J; Flenady, Vicki; Sienra-Monge, Juan JL (18 October 2006). "Immunostimulants for preventing respiratory tract infection in children". Cochrane Database of Systematic Reviews (4): CD004974. doi:10.1002/14651858.CD004974.pub2. PMID 17054227.
  13. ^ Grande, Antonio Jose; Keogh, Justin; Hoffmann, Tammy C; Beller, Elaine M; Del Mar, Chris B (16 June 2015). "Exercise versus no exercise for the occurrence, severity and duration of acute respiratory infections". Cochrane Database of Systematic Reviews (6): CD010596. doi:10.1002/14651858.CD010596.pub2. PMID 26077724.
  14. ^ a b c Moriyama, Miyu; Hugentobler, Walter J.; Iwasaki, Akiko (2020). "Seasonality of Respiratory Viral Infections". Annual Review of Virology. 7. doi:10.1146/annurev-virology-012420-022445. PMID 32196426. S2CID 214601321.

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