Medicine:Subclinical infection

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Short description: Nearly or completely asymptomatic infection
Typhoid Mary, pictured above in a 1909 tabloid, was a famous case of a subclinical infection of Salmonella enterica serovar.

A subclinical infection—sometimes called a preinfection or inapparent infection—is an infection by a pathogen that causes few or no signs or symptoms of infection in the host.[1] Subclinical infections can occur in both humans and animals.[2] Depending on the pathogen, which can be a virus or intestinal parasite, the host may be infectious and able to transmit the pathogen without ever developing symptoms;[3][4] such a host is called an asymptomatic carrier.[3] Many pathogens, including HIV, typhoid fever, and coronaviruses such as COVID-19 spread in their host populations through subclinical infection.[3][4][5]

Not all hosts of asymptomatic subclinical infections will become asymptomatic carriers. For example, hosts of Mycobacterium tuberculosis bacteria will only develop active tuberculosis in approximately one-tenth of cases;[6] the majority of those infected by Mtb bacteria have latent tuberculosis, a non-infectious type of tuberculosis that does not produce symptoms in individuals with sufficient immune responses.[7]

Because subclinical infections often occur without eventual overt sign, in some cases their presence is only identified by microbiological culture or DNA techniques such as polymerase chain reaction (PCR) tests.[8][9]

Transmission

In humans

Many pathogens are transmitted through their host populations by hosts with few or no symptoms, including sexually transmitted infections such as syphilis and genital warts.[10] In other cases, a host may develop more symptoms as the infection progresses beyond its incubation period.[3][7] These hosts create a natural reservoir of individuals that can transmit a pathogen to other individuals. Because cases often do not come to clinical attention, health statistics frequently are unable to measure the true prevalence of an infection in a population. This prevents accurate modeling of its transmissability.[11][12]

In animals

Some animal pathogens are also transmitted through subclinical infections. The A(H5) and A(H7) strains of avian influenza are divided into two categories: low pathogenicity avian influenza (LPAI) viruses, and highly pathogenic avian influenza (HPAI) viruses.[13] While HPAI viruses have a very high mortality rate for chickens,[14] LPAI viruses are very mild and produce few, if any symptoms; outbreaks in a flock may go undetected without ongoing testing.[14]

Wild ducks and other waterfowl are asymptomatic carriers of avian influenza, notably HPAI, and can be infected without showing signs of illness.[13][15] The prevalence of subclinical HPAI infection in waterfowl has contributed to the international outbreak of highly lethal H5N8 virus that began in early 2020.[13][16]

Pathogens known to cause subclinical infection

The following pathogens (together with their symptomatic illnesses) are known to be carried asymptomatically, often in a large percentage of the potential host population:


See also

References

  1. ↑ Porta, Miquel (2014). Oxford dictionary of epidemiology (6th ed.). Oxford: Oxford University Press. ISBN 978-0-19-997672-0. [page needed]
  2. ↑ Dimijian, Gregory G. (January 2000). "Pathogens and Parasites: Strategies and Challenges". Baylor University Medical Center Proceedings 13 (1): 19–29. doi:10.1080/08998280.2000.11927638. PMID 16389321. 
  3. ↑ 3.0 3.1 3.2 3.3 "Principles of Epidemiology | Lesson 1 - Section 9" (in en-us). 2021-12-20. https://www.cdc.gov/csels/dsepd/ss1978/lesson1/section9.html. 
  4. ↑ 4.0 4.1 Bogoch, Isaac (16 May 2020). "The Term 'Asymptomatic' Is More Complicated Than It Seems When It Comes To Coronavirus Infections". Forbes. https://www.forbes.com/sites/coronavirusfrontlines/2020/05/16/the-term-asymptomatic-is-more-complicated-than-it-seems-when-it-comes-to-coronavirus-infections/. 
  5. ↑ "Questions and Answers | Typhoid Fever | CDC" (in en-us). 2020-11-16. https://www.cdc.gov/typhoid-fever/sources.html. 
  6. ↑ "Tuberculosis (TB) Detailed Explanation". 2009-03-06. https://www.niaid.nih.gov/topics/tuberculosis/Understanding/WhatIsTB/pages/detailed.aspx. 
  7. ↑ 7.0 7.1 Drain, Paul K.; Bajema, Kristina L.; Dowdy, David; Dheda, Keertan; Naidoo, Kogieleum; Schumacher, Samuel G.; Ma, Shuyi; Meermeier, Erin et al. (2018-07-18). "Incipient and Subclinical Tuberculosis: a Clinical Review of Early Stages and Progression of Infection". Clinical Microbiology Reviews 31 (4): e00021–18. doi:10.1128/CMR.00021-18. ISSN 0893-8512. PMID 30021818. 
  8. ↑ Yang, S.; Rothman, R. E. (2004). "PCR-based diagnostics for infectious diseases: Uses, limitations, and future applications in acute-care settings". The Lancet. Infectious Diseases 4 (6): 337–348. doi:10.1016/S1473-3099(04)01044-8. PMID 15172342. 
  9. ↑ Miller, J. M.; Binnicker, M. J.; Campbell, S.; Carroll, K. C.; Chapin, K. C.; Gilligan, P. H.; Gonzalez, M. D.; Jerris, R. C. et al. (2018). "A Guide to Utilization of the Microbiology Laboratory for Diagnosis of Infectious Diseases: 2018 Update by the Infectious Diseases Society of America and the American Society for Microbiology". Clinical Infectious Diseases 67 (6): e1–e94. doi:10.1093/cid/ciy381. PMID 29955859. 
  10. ↑ Mayer, K. H.; Collis, T. K.; Celum, C. L. (15 February 2001). "The Clinical Manifestations and Treatment of Sexually Transmitted Diseases in Human Immunodeficiency Virus-Positive Men". Clinical Infectious Diseases 32 (4): 611–622. doi:10.1086/318722. PMID 11181126. 
  11. ↑ Van Seventer, Jean Maguire; Hochberg, Natasha S. (2017). "Principles of Infectious Diseases: Transmission, Diagnosis, Prevention, and Control". International Encyclopedia of Public Health. pp. 22–39. doi:10.1016/B978-0-12-803678-5.00516-6. ISBN 978-0-12-803708-9. 
  12. ↑ Ansumali, S.; Kaushal, S.; Kumar, A.; Prakash, M. K.; Vidyasagar, M. (2020). "Modelling a pandemic with asymptomatic patients, impact of lockdown and herd immunity, with applications to SARS-CoV-2". Annual Reviews in Control 50: 432–447. doi:10.1016/j.arcontrol.2020.10.003. PMID 33071595. 
  13. ↑ 13.0 13.1 13.2 CDC (2022-03-09). "Avian Influenza in Birds" (in en-us). https://www.cdc.gov/flu/avianflu/avian-in-birds.htm. 
  14. ↑ 14.0 14.1 "Avian influenza: assessing the pandemic threat". 2005. https://apps.who.int/iris/bitstream/handle/10665/68985/WHO_CDS_2005.29.pdf. 
  15. ↑ "Avian influenza in Canada". https://www.ducks.ca/our-work/waterfowl/avian-flu-in-canada/. 
  16. ↑ Government of Canada, Canadian Food Inspection Agency (2021-02-26). "Protect your flock from bird flu". https://www.inspection.gc.ca/eng/1614352583029/1614352660146. 
  17. ↑ Weinstein, Sara B.; Lake, Camille M.; Chastain, Holly M.; Fisk, David; Handali, Sukwan; Kahn, Philip L.; Montgomery, Susan P.; Wilkins, Patricia P. et al. (August 2017). "Seroprevalence of Baylisascaris procyonis Infection among Humans, Santa Barbara County, California, USA, 2014–2016". Emerging Infectious Diseases 23 (8): 1397–1399. doi:10.3201/eid2308.170222. PMID 28726612. 
  18. ↑ "Pertussis in soldiers, Israel". Emerging Infect. Dis. 11 (3): 506–8. March 2005. doi:10.3201/eid1103.040672. PMID 15789494. 
  19. ↑ "Chlamydia pneumoniae DNA in peripheral blood mononuclear cells in healthy control subjects and patients with diabetes mellitus, acute coronary syndrome, stroke, and arterial hypertension". Scand. J. Infect. Dis. 35 (10): 704–12. 2003. doi:10.1080/00365540310016538. PMID 14606608. 
  20. ↑ 20.0 20.1 Cecil, Jane A.; Howell, M. Rene; Tawes, Jennifer J.; Gaydos, Joel C.; McKee, Jr., Kelly T.; Quinn, Thomas C.; Gaydos, Charlotte A. (November 2001). "Features of Chlamydia trachomatis and Neisseria gonorrhoeae Infection in Male Army Recruits". The Journal of Infectious Diseases 184 (9): 1216–1219. doi:10.1086/323662. PMID 11598849. 
  21. ↑ 21.0 21.1 Korenromp, Eline L; Sudaryo, Mondastri K; de Vlas, Sake J; Gray, Ronald H; Sewankambo, Nelson K; Serwadda, David; Wawer, Maria J; Habbema, J Dik F (1 February 2002). "What proportion of episodes of gonorrhoea and chlamydia becomes symptomatic?". International Journal of STD & AIDS 13 (2): 91–101. doi:10.1258/0956462021924712. PMID 11839163. 
  22. ↑ "Prevalence and high rate of asymptomatic infection of Chlamydia trachomatis in male college Reserve Officer Training Corps cadets". Sex Transm Dis 30 (12): 901–4. December 2003. doi:10.1097/01.OLQ.0000091136.14932.8B. PMID 14646638. 
  23. ↑ "Prevalence of asymptomatic Clostridium difficile colonization in a nursing home population: a cross-sectional study". J Gend Specif Med 6 (2): 27–30. 2003. PMID 12813999. 
  24. ↑ "Prevalence and pathogenic role of Cyclospora cayetanensis in a Venezuelan community". Am. J. Trop. Med. Hyg. 68 (3): 304–6. March 2003. doi:10.4269/ajtmh.2003.68.304. PMID 12685635. 
  25. ↑ Burke, Donald S.; Scott, Robert McN.; Johnson, David E.; Nisalak, Ananda (1 January 1988). "A Prospective Study of Dengue Infections in Bangkok". The American Journal of Tropical Medicine and Hygiene 38 (1): 172–180. doi:10.4269/ajtmh.1988.38.172. INIST:7572063. PMID 3341519. 
  26. ↑ "Direct Amplification and Genotyping of Dientamoeba fragilis from Human Stool Specimens". J. Clin. Microbiol. 42 (2): 631–5. February 2004. doi:10.1128/JCM.42.2.631-635.2004. PMID 14766828. 
  27. ↑ Blessmann, Joerg; Ali, Ibne Karim M.; Ton Nu, Phuong A.; Dinh, Binh T.; Ngo Viet, Tram Q.; Le Van, An; Clark, C. Graham; Tannich, Egbert (October 2003). "Longitudinal Study of Intestinal Entamoeba histolytica Infections in Asymptomatic Adult Carriers". Journal of Clinical Microbiology 41 (10): 4745–4750. doi:10.1128/JCM.41.10.4745-4750.2003. PMID 14532214. 
  28. ↑ Wennerås, Christine; Erling, Valdemar (2004). "Prevalence of Enterotoxigenic Escherichia coli-associated Diarrhoea and Carrier State in the Developing World". Journal of Health, Population and Nutrition 22 (4): 370–382. PMID 15663170. 
  29. ↑ "Epstein-Barr Virus Infection in Ex Vivo Tonsil Epithelial Cell Cultures of Asymptomatic Carriers". J. Virol. 78 (22): 12613–24. November 2004. doi:10.1128/JVI.78.22.12613-12624.2004. PMID 15507648. 
  30. ↑ "The rate of asymptomatic throat carriage of group A Streptococcus in school children and associated ASO titers in Duzce, Turkey". Jpn. J. Infect. Dis. 57 (6): 271–2. December 2004. PMID 15623954. 
  31. ↑ "Effect of subclinical Helicobacter pylori infection on gastric wall thickness: multislice CT evaluation". Diagn Interv Radiol 14 (3): 138–42. September 2008. PMID 18814135. http://www.dirjournal.org/pubmed.php3?year=2008&volume=14&issue=3&page=138. 
  32. ↑ "Virologic characteristics of subclinical and symptomatic genital herpes infections". N. Engl. J. Med. 333 (12): 770–5. September 1995. doi:10.1056/NEJM199509213331205. PMID 7643884. 
  33. ↑ Mummidi, Srinivas; Ahuja, Seema S.; Gonalez, Enrique; Anderson, Stephanie A.; Santiago, Elvin N.; Stephan, Kevin T.; Craig, Fiona E.; O'Connell, Peter et al. (July 1998). "Genealogy of the CCR5 locus and chemokine system gene variants associated with altered rates of HIV-1 disease progression". Nature Medicine 4 (7): 786–793. doi:10.1038/nm0798-786. PMID 9662369. 
  34. ↑ "Incidence of Legionella pneumophila infections among Oklahoma pulmonary disease patients". J Natl Med Assoc 82 (1): 25–9. January 1990. PMID 2304095. 
  35. ↑ Anlar, B; Ayhan, A; Hotta, H; Itoh, M; Engin, D; Barun, S; Koseoglu, O (August 2002). "Measles Virus RNA in Tonsils of Asymptomatic Children". Journal of Paediatrics and Child Health 38 (4): 424–425. doi:10.1046/j.1440-1754.2002.t01-1-00029.x. PMID 12174013. 
  36. ↑ Beyene, D.; Aseffa, A.; Harboe, M.; Kidane, D.; Macdonald, M.; Klatser, P. R.; Bjune, G. A.; Smith, W. C. S. (October 2003). "Nasal carriage of Mycobacterium leprae DNA in healthy individuals in Lega Robi village, Ethiopia". Epidemiology and Infection 131 (2): 841–848. doi:10.1017/s0950268803001079. PMID 14596524. 
  37. ↑ "Consensus statement. Global burden of tuberculosis: estimated incidence, prevalence, and mortality by country. WHO Global Surveillance and Monitoring Project". JAMA 282 (7): 677–86. August 1999. doi:10.1001/jama.282.7.677. PMID 10517722. 
  38. ↑ "Neisseria meningitidis: an overview of the carriage state". J. Med. Microbiol. 53 (Pt 9): 821–32. September 2004. doi:10.1099/jmm.0.45529-0. INIST:16081902. PMID 15314188. 
  39. ↑ "Duration of nontyphoidal Salmonella carriage in asymptomatic adults". Clin. Infect. Dis. 38 (11): 1644–5. June 2004. doi:10.1086/421027. PMID 15156460. 
  40. ↑ "Asymptomatic and Symptomatic Excretion of Noroviruses during a Hospital Outbreak of Gastroenteritis". J. Clin. Microbiol. 42 (5): 2271–4. May 2004. doi:10.1128/JCM.42.5.2271-2274.2004. PMID 15131210. 
  41. ↑ "Predominance of rhinovirus in the nose of symptomatic and asymptomatic infants". Pediatr Allergy Immunol 14 (5): 363–70. October 2003. doi:10.1034/j.1399-3038.2003.00064.x. PMID 14641606. 
  42. ↑ "Typhoid fever". N. Engl. J. Med. 347 (22): 1770–82. November 2002. doi:10.1056/NEJMra020201. PMID 12456854. 
  43. ↑  , Wikidata Q84106604
  44. ↑ Fung, Sin-Yee; Yuen, Kit-San; Ye, Zi-Wei; Chan, Chi-Ping; Jin, Dong-Yan (1 January 2020). "A tug-of-war between severe acute respiratory syndrome coronavirus 2 and host antiviral defence: lessons from other pathogenic viruses". Emerging Microbes & Infections 9 (1): 558–570. doi:10.1080/22221751.2020.1736644. PMID 32172672. 
  45. ↑ Kenner, Julie; O'Connor, Tasha; Piantanida, Nicholas; Fishbain, Joel; Eberly, Bardwell; Viscount, Helen; Uyehara, Catherine; Hospenthal, Duane (June 2003). "Rates of Carriage of Methicillin-Resistant and Methicillin-Susceptible Staphylococcus aureus in an Outpatient Population". Infection Control & Hospital Epidemiology 24 (6): 439–444. doi:10.1086/502229. PMID 12828322. https://zenodo.org/record/1235696. 
  46. ↑ "A cross-sectional survey of the prevalence of Streptococcus pneumoniae nasopharyngeal carriage in Belgian infants attending day care centres". Clin. Microbiol. Infect. 10 (9): 797–803. September 2004. doi:10.1111/j.1198-743X.2004.00926.x. PMID 15355410. 
  47. ↑ "Syphilis: Review with Emphasis on Clinical, Epidemiologic, and Some Biologic Features". Clin. Microbiol. Rev. 12 (2): 187–209. April 1999. doi:10.1128/CMR.12.2.187. PMID 10194456. 

Further reading



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