Subclinical 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 that, being subclinical, is nearly or completely asymptomatic (no signs or symptoms).[1] A subclinically infected person is thus a paucisymptomatic or asymptomatic carrier of a microbe, intestinal parasite, or virus that usually is a pathogen causing illness, at least in some individuals. Many pathogens spread by being silently carried in this way by some of their host population. Such infections occur both in humans and animals.

An example of an asymptomatic infection is a mild common cold that is not noticed by the infected individual. Since subclinical infections often occur without eventual overt sign, their existence is only identified by microbiological culture or DNA techniques such as polymerase chain reaction.

Infection transmission/signs

An individual may only develop signs of an infection after a period of subclinical infection, a duration that is called the incubation period. This is the case, for example, for subclinical sexually transmitted diseases such as AIDS and genital warts. It is thought that individuals with such subclinical infections, and those that never develop overt illness, creates a reserve of individuals that can transmit an infectious agent to infect other individuals. Because such cases of infections do not come to clinical attention, health statistics can often fail to measure the true prevalence of an infection in a population, and this prevents the accurate modeling of its infectious transmission.

Types of subclinical infections

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

Host tolerance

Fever and sickness behavior and other signs of infection are often taken to be due to them. However, they are evolved physiological and behavioral responses of the host to clear itself of the infection. Instead of incurring the costs of deploying these evolved responses to infections, the body opts to tolerate an infection[33] as an alternative to seeking to control or remove the infecting pathogen.[34]

Subclinical infections are important since they allow infections to spread from a reserve of carriers. They also can cause clinical problems unrelated to the direct issue of infection. For example, in the case of urinary tract infections in women, this infection may cause preterm delivery if the person becomes pregnant without proper treatment.[35]

See also

References

  1. ↑ Porta, Miquel (2014). Oxford dictionary of epidemiology (6th ed.). Oxford: Oxford University Press. ISBN 9780199976720.
  2. ↑ Weinstein, Sara B.; Lake, Camille M.; Chastain, Holly M.; Fisk, David; Handali, Sukwan; Kahn, Philip L.; Montgomery, Susan P.; Wilkins, Patricia P.; Kuris, Armand M.; Lafferty, Kevin D. (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. ISSN 1080-6040. PMC 5547801. PMID 28726612.
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  4. ↑ Müller J, Møller DS, Kjaer M, Nyvad O, Larsen NA, Pedersen EB (2003). "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. doi:10.1080/00365540310016538. PMID 14606608. S2CID 43211363.
  5. 1 2 Cecil JA, Howell MR, Tawes JJ, et al. (November 2001). "Features of Chlamydia trachomatis and Neisseria gonorrhoeae infection in male Army recruits". J. Infect. Dis. 184 (9): 1216–9. doi:10.1086/323662. PMID 11598849.
  6. 1 2 Korenromp EL, Sudaryo MK, de Vlas SJ, et al. (February 2002). "What proportion of episodes of gonorrhoea and chlamydia becomes symptomatic?". Int J STD AIDS. 13 (2): 91–101. doi:10.1258/0956462021924712. PMID 11839163. S2CID 33926189.
  7. ↑ Sutton TL, Martinko T, Hale S, Fairchok MP (December 2003). "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. doi:10.1097/01.OLQ.0000091136.14932.8B. PMID 14646638. S2CID 43394485.
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  16. ↑ Kul S, Sert B, Sari A, et al. (September 2008). "Effect of subclinical Helicobacter pylori infection on gastric wall thickness: multislice CT evaluation". Diagn Interv Radiol. 14 (3): 138–42. PMID 18814135.
  17. ↑ Wald A, Zeh J, Selke S, Ashley RL, Corey L (September 1995). "Virologic characteristics of subclinical and symptomatic genital herpes infections". N. Engl. J. Med. 333 (12): 770–5. doi:10.1056/NEJM199509213331205. PMID 7643884.
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Further reading

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