incubation period

{{short description|Time between infection and the onset of disease symptoms}}

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.[https://www.cdc.gov/csels/dsepd/ss1978/lesson1/section9.html Lesson 1, Section 9: Natural History and Spectrum of Disease], Principles of Epidemiology in Public Health Practice, Third Edition, An Introduction to Applied Epidemiology and Biostatistics, Centers for Disease Control and Prevention, May 18, 2012 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.{{cite journal |pmid=9305294 |year=1997 |last1=Sharara |first1=A. I. |title=Chronic hepatitis C |journal=Southern Medical Journal |volume=90 |issue=9 |pages=872–7 |doi=10.1097/00007611-199709000-00002|s2cid=9838013 }} 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.{{cn|date=June 2022}}

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.{{cn|date=June 2022}}

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.{{cite journal|last1=Chan|first1=Miranda|last2=Johansson|first2=Michael A.|title=The Incubation Periods of Dengue Viruses|journal=PLOS ONE|date=Nov 30, 2012|volume=7|doi=10.1371/journal.pone.0050972|pmc=3511440|pmid=23226436|pages=e50972|issue=11|bibcode=2012PLoSO...750972C|doi-access=free}}

Determining factors

The specific incubation period for a disease process is the result of multiple factors, including:{{cn|date=June 2022}}

Dose or inoculum of an infectious agent
Route of inoculation
Rate of replication of infectious agent
Host susceptibility
Immune response

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
class="wikitable sortable" title="Disease incubation periods"
Cellulitis caused by Pasteurella multocida	0 days[http://kidshealth.org/parent/infections/skin/cellulitis.html Cellulitis], kidshealth.org. Accessed 2012-05-28.	1 day
Chicken pox	9 days{{Cite journal \|date=March 22, 2020 \|title=Chickenpox: Practice Essentials, Background, Pathophysiology \|url=https://emedicine.medscape.com/article/1131785-overview \|via=eMedicine}}	21 days
Cholera	0.5 days{{cite journal \|last1=Azman \|first1=Andrew S. \|last2=Rudolph \|first2=Kara E. \|last3=Cummings \|first3=Derek A.T. \|last4=Lessler \|first4=Justin \|year=2013 \|title=The incubation period of cholera: A systematic review \|journal=Journal of Infection \|volume=66 \|issue=5 \|pages=432–8 \|doi=10.1016/j.jinf.2012.11.013 \|pmc=3677557 \|pmid=23201968}}	4.5 days
Common cold	1 day{{cite journal \|last1=Lessler \|first1=Justin \|last2=Reich \|first2=Nicholas G \|last3=Brookmeyer \|first3=Ron \|last4=Perl \|first4=Trish M \|last5=Nelson \|first5=Kenrad E \|last6=Cummings \|first6=Derek AT \|year=2009 \|title=Incubation periods of acute respiratory viral infections: A systematic review \|journal=The Lancet Infectious Diseases \|volume=9 \|issue=5 \|pages=291–300 \|doi=10.1016/S1473-3099(09)70069-6 \|pmc=4327893 \|pmid=19393959}}[http://www.mayoclinic.com/health/common-cold/DS00056/DSECTION=symptoms Common cold], The Mayo Clinic, mayoclinic.com. Accessed 2012-05-28.	3 days
COVID-19	2 days {{cite journal \|last1=Linton \|first1=Natalie M. \|last2=Kobayashi \|first2=Tetsuro G \|last3=Yang \|first3=Yichi \|last4=Hayashi \|first4=Katsuma M \|last5=Akhmetzhanov \|first5=Andrei R. E \|last6=Jung \|first6=Sung-mok \|last7=Yuan \|first7=Baoyin \|last8=Kinoshita \|first8=Ryo \|last9=Nishiura1 \|first9=Hiroshi \|year=2020 \|title=Incubation Period and Other Epidemiological Characteristics of 2019 Novel Coronavirus Infections with Right Truncation: A Statistical Analysis of Publicly Available Case Data \|journal=J Clin Med \|volume=9 \|issue=2 \|pages=538 \|doi=10.3390/jcm9020538 \|pmc=7074197 \|pmid=32079150 \|doi-access=free}}	11.5{{Cite journal\|title=The Incubation Period of Coronavirus Disease 2019 (COVID-19) From Publicly Reported Confirmed Cases: Estimation and Application\|first1=Stephen A.\|last1=Lauer\|first2=Kyra H.\|last2=Grantz\|first3=Qifang\|last3=Bi\|first4=Forrest K.\|last4=Jones\|first5=Qulu\|last5=Zheng\|first6=Hannah R.\|last6=Meredith\|first7=Andrew S.\|last7=Azman\|first8=Nicholas G.\|last8=Reich\|first9=Justin\|last9=Lessler\|date=March 10, 2020\|journal=Annals of Internal Medicine\|volume=172\|issue=9\|pages=577–582\|doi=10.7326/M20-0504\|pmid=32150748\|pmc=7081172}}/12.5{{Cite journal\|title=Early Transmission Dynamics in Wuhan, China, of Novel Coronavirus–Infected Pneumonia\|first1=Qun\|last1=Li\|first2=Xuhua\|last2=Guan\|first3=Peng\|last3=Wu\|first4=Xiaoye\|last4=Wang\|first5=Lei\|last5=Zhou\|first6=Yeqing\|last6=Tong\|first7=Ruiqi\|last7=Ren\|first8=Kathy S.M.\|last8=Leung\|first9=Eric H.Y.\|last9=Lau\|first10=Jessica Y.\|last10=Wong\|first11=Xuesen\|last11=Xing\|first12=Nijuan\|last12=Xiang\|first13=Yang\|last13=Wu\|first14=Chao\|last14=Li\|first15=Qi\|last15=Chen\|first16=Dan\|last16=Li\|first17=Tian\|last17=Liu\|first18=Jing\|last18=Zhao\|first19=Man\|last19=Liu\|first20=Wenxiao\|last20=Tu\|first21=Chuding\|last21=Chen\|first22=Lianmei\|last22=Jin\|first23=Rui\|last23=Yang\|first24=Qi\|last24=Wang\|first25=Suhua\|last25=Zhou\|first26=Rui\|last26=Wang\|first27=Hui\|last27=Liu\|first28=Yinbo\|last28=Luo\|first29=Yuan\|last29=Liu\|first30=Ge\|last30=Shao\|first31=Huan\|last31=Li\|first32=Zhongfa\|last32=Tao\|first33=Yang\|last33=Yang\|first34=Zhiqiang\|last34=Deng\|first35=Boxi\|last35=Liu\|first36=Zhitao\|last36=Ma\|first37=Yanping\|last37=Zhang\|first38=Guoqing\|last38=Shi\|first39=Tommy T.Y.\|last39=Lam\|first40=Joseph T.\|last40=Wu\|first41=George F.\|last41=Gao\|first42=Benjamin J.\|last42=Cowling\|first43=Bo\|last43=Yang\|first44=Gabriel M.\|last44=Leung\|first45=Zijian\|last45=Feng\|date=March 26, 2020\|journal=New England Journal of Medicine\|volume=382\|issue=13\|pages=1199–1207\|doi=10.1056/NEJMoa2001316\|pmid=31995857\|pmc=7121484}}/14 days
Dengue fever	3 days{{cite journal \|last1=Gubler \|first1=D. J. \|year=1998 \|title=Dengue and dengue hemorrhagic fever \|journal=Clinical Microbiology Reviews \|volume=11 \|issue=3 \|pages=480–96 \|doi=10.1128/CMR.11.3.480 \|pmc=88892 \|pmid=9665979}}	14 days
Ebola	1 day[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?], World Health Organization, who.int. Accessed 2014-10-21.	21 (95%), 42 (98%) days
Erythema infectiosum (Fifth disease)	13 days{{EMedicine\|article\|801732\|Erythema Infectiosum}}	18 days
Giardia	3 days	21 days
HIV	data-sort-value="14"\|2 weeks to months, or longer{{cite journal \|last1=Kahn \|first1=James O. \|last2=Walker \|first2=Bruce D. \|year=1998 \|title=Acute Human Immunodeficiency Virus Type 1 Infection \|journal=New England Journal of Medicine \|volume=339 \|issue=1 \|pages=33–9 \|doi=10.1056/NEJM199807023390107 \|pmid=9647878}}	data-sort-value="21"\|3 weeks to months, or longer
Infectious mononucleosis (glandular fever)	28 daysMacnair, Trisha, [https://www.bbc.co.uk/health/physical_health/conditions/glandularfever2.shtml Glandular fever], BBC, bbc.co.uk. Accessed 2012-05-28.	42 days
Influenza	1 day[https://www.cdc.gov/flu/ Seasonal Influenza (Flu)], Centers for Disease Control and Prevention, cdc.gov. Accessed 2012-05-28.	3 days
Kuru disease	data-sort-value="3760"\|10.3 years (mean){{cite journal \|last1=Huillard d'Aignaux \|first1=J. N. \|last2=Cousens \|first2=S. N. \|last3=MacCario \|first3=J \|last4=Costagliola \|first4=D \|last5=Alpers \|first5=M. P. \|last6=Smith \|first6=P. G. \|last7=Alpérovitch \|first7=A \|year=2002 \|title=The incubation period of kuru \|journal=Epidemiology \|volume=13 \|issue=4 \|pages=402–8 \|doi=10.1097/00001648-200207000-00007 \|pmid=12094094 \|s2cid=22810508 \|doi-access=free}}	data-sort-value="4820"\|13.2 years
Leprosy	data-sort-value="365"\|1 year{{cite web \|date=January 2014 \|title=Leprosy Fact sheet N°101 \|url=https://www.who.int/mediacentre/factsheets/fs101/en/ \|url-status=live \|archive-url=https://web.archive.org/web/20131212084309/http://www.who.int/mediacentre/factsheets/fs101/en/ \|archive-date=2013-12-12 \|work=World Health Organization}}	data-sort-value="7300"\|20 or more years
Marburg	5 days[https://www.cdc.gov/ncidod/dvrd/spb/mnpages/dispages/marburg/qa.htm Questions and Answers About Marburg Hemorrhagic Fever] {{webarchive\|url=https://web.archive.org/web/20160303210321/http://www.cdc.gov/ncidod/dvrd/spb/mnpages/dispages/marburg/qa.htm\|date=2016-03-03}}, Centers for Disease Control and Prevention, cdc.gov. Accessed 2012-05-28.	10 days
Measles	9 days[http://www.aocd.org/skin/dermatologic_diseases/measles.html Measles], American Osteopathic College of Dermatology, aocd.org. Accessed 2012-05-28.	12 days
MERS	2 days{{cite web \|date=2 August 2019 \|title=MERS Clinical Features \|url=https://www.cdc.gov/coronavirus/mers/clinical-features.html \|access-date=22 March 2020 \|website=CDC.gov \|publisher=CDC}}	14 days
Mumps	14 days[http://www.vaccineinformation.org/mumps/qandadis.asp Mumps Disease, Questions & Answers] {{webarchive\|url=https://web.archive.org/web/20071120094122/http://www.vaccineinformation.org/mumps/qandadis.asp\|date=2007-11-20}}, vaccineinformation.org. Accessed 2012-05-28.	18 days
Norovirus	1 day[https://www.cdc.gov/norovirus/index.html Norovirus], Centers for Disease Control and Prevention, cdc.gov. Accessed 2012-05-28.	2 days
Pertussis (whooping cough)	7 days[http://www.gpnotebook.co.uk/simplepage.cfm?ID=-1751515131 Pertussis], GPnotebook, gpnotebook.co.uk. Accessed 2012-05-28.	14 days
Polio	7 days[http://www.gpnotebook.co.uk/simplepage.cfm?ID=1765081109 Polio], GPnotebook, gpnotebook.co.uk. Accessed 2012-05-28.	14 days
Rabies	1 months, but may vary from <1 week to rarely >1 year.{{cite web \|title=WHO - Rabies \|url=https://www.who.int/mediacentre/factsheets/fs099/en/ \|work=who.int}}{{Cite web \|date=April 2018 \|title=Rabies vaccines: WHO position paper – April 2018 \|url=https://apps.who.int/iris/bitstream/handle/10665/272372/WER9316-201-219.pdf \|website=WHO \|via=apps.who.int}}	3 months
Rocky Mountain spotted fever	2 days[http://dermatology.about.com/cs/infectionbacteria/a/rmsf.htm Rocky Mountain Spotted Fever] {{Webarchive\|url=https://web.archive.org/web/20160304053452/http://dermatology.about.com/cs/infectionbacteria/a/rmsf.htm \|date=2016-03-04 }}, About.com. Accessed 2012-05-28.	14 days
Roseola	5 days{{EMedicine\|article\|1133023\|Roseola Infantum}}	15 days
Rubella (German measles)	14 days{{EMedicine\|article\|1133108\|Dermatologic Manifestations of Rubella}}	21 days
Salmonella	12 days	24 days
Scarlet fever	1 day{{EMedicine\|article\|1053253\|Scarlet Fever}}	4 days
SARS	1 dayWorld Health Organization (WHO), [https://www.who.int/topics/sars/en/ Severe acute respiratory syndrome], www.who.int. Accessed 2012-05-28.	10 days
Smallpox	7 days[http://www.bt.cdc.gov/agent/smallpox/overview/disease-facts.asp Smallpox Disease Overview] {{webarchive\|url=https://web.archive.org/web/20130402220850/http://www.bt.cdc.gov/agent/smallpox/overview/disease-facts.asp\|date=2013-04-02}}, Centers for Disease Control and Prevention, cdc.gov. Accessed 2012-05-28.	17 days
Tetanus	7 days{{EMedicine\|article\|229594\|Tetanus}}	21 days
Tuberculosis	data-sort-value="14"\|2 weeks{{cite web \|title=Tuberculosis (TB) \|url=https://www.medicinenet.com/tuberculosis_tb_facts/article.htm#how_do_physicians_diagnose_tuberculosis_what_is_involved_with_tb_testing \|access-date=22 March 2020 \|website=MedicineNet }}	data-sort-value="84"\|12 weeks
Typhoid	7 days	21 days

References

Category:Epidemiology

Category:Infectious diseases

incubation period

Intrinsic and extrinsic incubation period

Determining factors

Examples for diseases in humans

See also

References