Incubation period explained

Incubation period (also known as the latent period or latency period) is the time elapsed between exposure to a pathogenic organism, a chemical, or radiation, and when symptoms and signs are first apparent.[1] In a typical infectious disease, the incubation period signifies the period taken by the multiplying organism to reach a threshold necessary to produce symptoms in the host.

While latent or latency period may be synonymous, a distinction is sometimes made whereby the latent period is defined as the time from infection to infectiousness. Which period is shorter depends on the disease. A person may carry a disease, such as Streptococcus in the throat, without exhibiting any symptoms. Depending on the disease, the person may or may not be contagious during the incubation period.

During latency, an infection is subclinical. With respect to viral infections, in incubation the virus is replicating.[2] This is in contrast to viral latency, a form of dormancy in which the virus does not replicate. An example of latency is HIV infection. HIV may at first have no symptoms and show no signs of AIDS, despite HIV replicating in the lymphatic system and rapidly accumulating a large viral load. People with HIV in this stage may be infectious.

Intrinsic and extrinsic incubation period

The terms "intrinsic incubation period" and "extrinsic incubation period" are used in vector-borne diseases. The intrinsic incubation period is the time taken by an organism to complete its development in the definitive host. The extrinsic incubation period is the time taken by an organism to develop in the intermediate host.

For example, once ingested by a mosquito, malaria parasites must undergo development within the mosquito before they are infectious to humans. The time required for development in the mosquito ranges from 10 to 28 days, depending on the parasite species and the temperature. This is the extrinsic incubation period of that parasite. If a female mosquito does not survive longer than the extrinsic incubation period, then she will not be able to transmit any malaria parasites.

But if a mosquito successfully transfers the parasite to a human body via a bite, the parasite starts developing. The time between the injection of the parasite into the human and the development of the first symptoms of malaria is its intrinsic incubation period.[3]

Determining factors

The specific incubation period for a disease process is the result of multiple factors, including:

Examples for diseases in humans

Due to inter-individual variation, the incubation period is always expressed as a range. When possible, it is best to express the mean and the 10th and 90th percentiles, though this information is not always available.

For many conditions, incubation periods are longer in adults than they are in children or infants.

Disease between and
Cellulitis caused by Pasteurella multocida 0 days[4] 1 day
9 days[5] 21 days
0.5 days[6] 4.5 days
1 day[7] [8] 3 days
2 days [9] 11.5[10] /12.5[11] /14 days
3 days[12] 14 days
1 day[13] 21 (95%), 42 (98%) days
Erythema infectiosum (Fifth disease) 13 days18 days
3 days 21 days
data-sort-value="14"2 weeks to months, or longer[14] data-sort-value="21"3 weeks to months, or longer
Infectious mononucleosis (glandular fever) 28 days[15] 42 days
1 day[16] 3 days
data-sort-value="3760"10.3 years (mean)[17] data-sort-value="4820"13.2 years
data-sort-value="365"1 year[18] data-sort-value="7300"20 or more years
5 days[19] 10 days
9 days[20] 12 days
2 days[21] 14 days
14 days[22] 18 days
1 day[23] 2 days
Pertussis (whooping cough) 7 days[24] 14 days
7 days[25] 14 days
1 months, but may vary from <1 week to rarely >1 year.[26] [27] 3 months
2 days[28] 14 days
5 days15 days
Rubella (German measles) 14 days21 days
12 days24 days
1 day4 days
1 day[29] 10 days
7 days[30] 17 days
7 days21 days
data-sort-value="14"2 weeks[31] data-sort-value="84"12 weeks
7 days 21 days

See also

Notes and References

  1. https://www.cdc.gov/csels/dsepd/ss1978/lesson1/section9.html Lesson 1, Section 9: Natural History and Spectrum of Disease
  2. 9305294 . 1997 . Sharara . A. I. . Chronic hepatitis C . Southern Medical Journal . 90 . 9 . 872–7 . 10.1097/00007611-199709000-00002. 9838013 .
  3. Chan. Miranda. Johansson. Michael A.. The Incubation Periods of Dengue Viruses. PLOS ONE. Nov 30, 2012. 7. 10.1371/journal.pone.0050972. 3511440. 23226436. e50972. 11. 2012PLoSO...750972C. free.
  4. http://kidshealth.org/parent/infections/skin/cellulitis.html Cellulitis
  5. March 22, 2020 . Chickenpox: Practice Essentials, Background, Pathophysiology . eMedicine.
  6. Azman . Andrew S. . Rudolph . Kara E. . Cummings . Derek A.T. . Lessler . Justin . 2013 . The incubation period of cholera: A systematic review . Journal of Infection . 66 . 5 . 432–8 . 10.1016/j.jinf.2012.11.013 . 3677557 . 23201968.
  7. Lessler . Justin . Reich . Nicholas G . Brookmeyer . Ron . Perl . Trish M . Nelson . Kenrad E . Cummings . Derek AT . 2009 . Incubation periods of acute respiratory viral infections: A systematic review . The Lancet Infectious Diseases . 9 . 5 . 291–300 . 10.1016/S1473-3099(09)70069-6 . 4327893 . 19393959.
  8. http://www.mayoclinic.com/health/common-cold/DS00056/DSECTION=symptoms Common cold
  9. Linton . Natalie M. . Kobayashi . Tetsuro G . Yang . Yichi . Hayashi . Katsuma M . Akhmetzhanov . Andrei R. E . Jung . Sung-mok . Yuan . Baoyin . Kinoshita . Ryo . Nishiura1 . Hiroshi . 2020 . Incubation Period and Other Epidemiological Characteristics of 2019 Novel Coronavirus Infections with Right Truncation: A Statistical Analysis of Publicly Available Case Data . J Clin Med . 9 . 2 . 538 . 10.3390/jcm9020538 . 7074197 . 32079150 . free.
  10. The Incubation Period of Coronavirus Disease 2019 (COVID-19) From Publicly Reported Confirmed Cases: Estimation and Application. Stephen A.. Lauer. Kyra H.. Grantz. Qifang. Bi. Forrest K.. Jones. Qulu. Zheng. Hannah R.. Meredith. Andrew S.. Azman. Nicholas G.. Reich. Justin. Lessler. March 10, 2020. Annals of Internal Medicine. 172. 9. 577–582. 10.7326/M20-0504. 32150748. 7081172.
  11. Early Transmission Dynamics in Wuhan, China, of Novel Coronavirus–Infected Pneumonia. Qun. Li. Xuhua. Guan. Peng. Wu. Xiaoye. Wang. Lei. Zhou. Yeqing. Tong. Ruiqi. Ren. Kathy S.M.. Leung. Eric H.Y.. Lau. Jessica Y.. Wong. Xuesen. Xing. Nijuan. Xiang. Yang. Wu. Chao. Li. Qi. Chen. Dan. Li. Tian. Liu. Jing. Zhao. Man. Liu. Wenxiao. Tu. Chuding. Chen. Lianmei. Jin. Rui. Yang. Qi. Wang. Suhua. Zhou. Rui. Wang. Hui. Liu. Yinbo. Luo. Yuan. Liu. Ge. Shao. Huan. Li. Zhongfa. Tao. Yang. Yang. Zhiqiang. Deng. Boxi. Liu. Zhitao. Ma. Yanping. Zhang. Guoqing. Shi. Tommy T.Y.. Lam. Joseph T.. Wu. George F.. Gao. Benjamin J.. Cowling. Bo. Yang. Gabriel M.. Leung. Zijian. Feng. March 26, 2020. New England Journal of Medicine. 382. 13. 1199–1207. 10.1056/NEJMoa2001316. 31995857. 7121484.
  12. Gubler . D. J. . 1998 . Dengue and dengue hemorrhagic fever . Clinical Microbiology Reviews . 11 . 3 . 480–96 . 10.1128/CMR.11.3.480 . 88892 . 9665979.
  13. https://web.archive.org/web/20141014192416/http://www.who.int/mediacentre/news/ebola/14-october-2014/en/ Are the Ebola outbreaks in Nigeria and Senegal over?
  14. Kahn . James O. . Walker . Bruce D. . 1998 . Acute Human Immunodeficiency Virus Type 1 Infection . New England Journal of Medicine . 339 . 1 . 33–9 . 10.1056/NEJM199807023390107 . 9647878.
  15. Macnair, Trisha, Glandular fever, BBC, bbc.co.uk. Accessed 2012-05-28.
  16. https://www.cdc.gov/flu/ Seasonal Influenza (Flu)
  17. Huillard d'Aignaux . J. N. . Cousens . S. N. . MacCario . J . Costagliola . D . Alpers . M. P. . Smith . P. G. . Alpérovitch . A . 2002 . The incubation period of kuru . Epidemiology . 13 . 4 . 402–8 . 10.1097/00001648-200207000-00007 . 12094094 . 22810508 . free.
  18. Web site: January 2014 . Leprosy Fact sheet N°101 . live . https://web.archive.org/web/20131212084309/http://www.who.int/mediacentre/factsheets/fs101/en/ . 2013-12-12 . World Health Organization.
  19. https://www.cdc.gov/ncidod/dvrd/spb/mnpages/dispages/marburg/qa.htm Questions and Answers About Marburg Hemorrhagic Fever
  20. http://www.aocd.org/skin/dermatologic_diseases/measles.html Measles
  21. Web site: 2 August 2019 . MERS Clinical Features . 22 March 2020 . CDC.gov . CDC.
  22. http://www.vaccineinformation.org/mumps/qandadis.asp Mumps Disease, Questions & Answers
  23. https://www.cdc.gov/norovirus/index.html Norovirus
  24. http://www.gpnotebook.co.uk/simplepage.cfm?ID=-1751515131 Pertussis
  25. http://www.gpnotebook.co.uk/simplepage.cfm?ID=1765081109 Polio
  26. Web site: WHO - Rabies . who.int.
  27. Web site: April 2018 . Rabies vaccines: WHO position paper – April 2018 . . apps.who.int.
  28. http://dermatology.about.com/cs/infectionbacteria/a/rmsf.htm Rocky Mountain Spotted Fever
  29. [World Health Organization]
  30. http://www.bt.cdc.gov/agent/smallpox/overview/disease-facts.asp Smallpox Disease Overview
  31. Web site: Tuberculosis (TB) . 22 March 2020 . MedicineNet .

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