{{short description|Time between infection and the onset of disease symptoms}} thumbnail|In some diseases, as depicted in this diagram, the latency period is shorter than the incubation period. After the latency period (but before clinical infection) the infected person can transmit the disease without signs of any symptoms. Such infection is called subclinical infection.
'''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.<ref>[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</ref> 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.<ref name="pmid9305294">{{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 }}</ref> 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.<ref>{{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|article-number=e50972|issue=11|bibcode=2012PLoSO...750972C|doi-access=free}}</ref>
==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.
{| class="wikitable sortable" title="Disease incubation periods" |- ! Disease !! between !! and |- | Cellulitis caused by ''Pasteurella multocida'' ||0 days<ref>[http://kidshealth.org/parent/infections/skin/cellulitis.html Cellulitis], kidshealth.org. Accessed 2012-05-28.</ref>||1 day |- | Chicken pox ||9 days<ref>{{Cite journal |date=March 22, 2020 |title=Chickenpox: Practice Essentials, Background, Pathophysiology |url=https://emedicine.medscape.com/article/1131785-overview |via=eMedicine}}</ref>||21 days |- | Cholera ||0.5 days<ref>{{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}}</ref>||4.5 days |- | Common cold ||1 day<ref>{{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}}</ref><ref>[http://www.mayoclinic.com/health/common-cold/DS00056/DSECTION=symptoms Common cold], The Mayo Clinic, mayoclinic.com. Accessed 2012-05-28.</ref>||3 days |- | COVID-19 ||2 days <ref>{{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 |page=538 |doi=10.3390/jcm9020538 |pmc=7074197 |pmid=32079150 |doi-access=free}}</ref>||11.5<ref>{{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}}</ref>/12.5<ref>{{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}}</ref>/14 days |- | Dengue fever ||3 days<ref>{{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}}</ref>||14 days |- | Ebola ||1 day<ref>[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.</ref>||21 (95%), 42 (98%) days
|- | Erythema infectiosum (Fifth disease) ||13 days<ref>{{EMedicine|article|801732|Erythema Infectiosum}}</ref>||18 days |- | Giardia ||3 days ||21 days |- | HIV ||data-sort-value="14"|2 weeks to months, or longer<ref>{{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}}</ref>||data-sort-value="21"|3 weeks to months, or longer |- | Infectious mononucleosis (glandular fever) ||28 days<ref>Macnair, Trisha, [https://web.archive.org/web/20100329214024/http://www.bbc.co.uk/health/physical_health/conditions/glandularfever2.shtml Glandular fever], BBC, bbc.co.uk. Accessed 2012-05-28.</ref>||42 days |- | Influenza ||1 day<ref>[https://www.cdc.gov/flu/ Seasonal Influenza (Flu)], Centers for Disease Control and Prevention, cdc.gov. Accessed 2012-05-28.</ref>||3 days |- | Kuru disease ||data-sort-value="3760"|10.3 years (mean)<ref name="pmid12094094">{{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}}</ref>||data-sort-value="4820"|13.2 years |- | Leprosy ||data-sort-value="365"|1 year<ref>{{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}}</ref>||data-sort-value="7300"|20 or more years |- | Marburg ||5 days<ref>[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.</ref>||10 days |- | Measles ||9 days<ref>[http://www.aocd.org/skin/dermatologic_diseases/measles.html Measles], American Osteopathic College of Dermatology, aocd.org. Accessed 2012-05-28.</ref>||12 days |- | MERS ||2 days<ref name="CDC MERS Incubation">{{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}}</ref>||14 days |- | Mumps ||14 days<ref>[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.</ref>||18 days |- | Norovirus ||1 day<ref>[https://www.cdc.gov/norovirus/index.html Norovirus], Centers for Disease Control and Prevention, cdc.gov. Accessed 2012-05-28.</ref>||2 days |- | Pertussis (whooping cough) ||7 days<ref>[http://www.gpnotebook.co.uk/simplepage.cfm?ID=-1751515131 Pertussis], GPnotebook, gpnotebook.co.uk. Accessed 2012-05-28.</ref>||14 days |- | Polio ||7 days<ref>[http://www.gpnotebook.co.uk/simplepage.cfm?ID=1765081109 Polio], GPnotebook, gpnotebook.co.uk. Accessed 2012-05-28.</ref>||14 days |- | Rabies ||1 month, but may vary from <1 week to rarely >1 year.<ref>{{cite web |title=WHO - Rabies |url=https://www.who.int/mediacentre/factsheets/fs099/en/ |work=who.int}}</ref><ref>{{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}}</ref>||3 months |- | Rocky Mountain spotted fever ||2 days<ref>[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.</ref>||14 days |- | Roseola ||5 days<ref>{{EMedicine|article|1133023|Roseola Infantum}}</ref>||15 days |- | Rubella (German measles) ||14 days<ref name=":0">{{EMedicine|article|1133108|Dermatologic Manifestations of Rubella}}</ref>||21 days |- | Salmonella ||12 days<ref name=":0" />||24 days |- | Scarlet fever ||1 day<ref>{{EMedicine|article|1053253|Scarlet Fever}}</ref>||4 days |- | SARS ||1 day<ref>World Health Organization (WHO), [https://www.who.int/topics/sars/en/ Severe acute respiratory syndrome], www.who.int. Accessed 2012-05-28.</ref>||10 days |- | Smallpox ||7 days<ref>[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.</ref>||17 days |- | Tetanus ||7 days<ref>{{EMedicine|article|229594|Tetanus}}</ref>||21 days |- | Tuberculosis ||data-sort-value="14"|2 weeks<ref name="MedicineNet TB Incubation">{{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 }}</ref>||data-sort-value="84"|12 weeks |- | Typhoid ||7 days ||21 days |}
==See also== {{Scholia}} * Latent period * Infectious period * Gestation period * Prodrome * Quarantine * Window period, the time between infection and when lab tests can identify the infection.
==References== {{reflist}} {{Concepts in infectious disease}}
Category:Epidemiology Category:Infectious diseases