基本传染数

**部分被人广泛知悉疾病的 $R_{0}$ 值**^[1]
疾病	传播途径	$R_{0}$
麻疹	空气传播	12–18
白喉	唾液	6-7
天花	空气传播、飞沫传播	5–7
脊髓灰质炎	粪口传播	5–7
风疹	空气传播、飞沫传播	5–7
流行性腮腺炎	呼吸道飞沫	10–12^[2]
HIV/AIDS	性传播	4.5 (只算非洲（英语：HIV/AIDS in Africa）) ^[3]
百日咳	空气传播、飞沫传播	5.5^[4]
SARS	空气传播、飞沫传播、粪口传播	2-5^[5]^{[注 1]}
流行性感冒（1918年流感大流行）	空气传播、飞沫传播	2–3^[7]
伊波拉出血热（西非伊波拉病毒疫症）	体液传播	1.5-2.5^[8]
COVID-19	飞沫传播、接触传播、粪口传播	1.4-3.8 ^[9] 3.8–8.9（截至2020年6月）^[10] Delta变异株：5.1 ^[11] Alpha变异株：4–5 ^[12] Omicron变异株：7 ^[13]
中东呼吸综合征	呼吸道飞沫	0.5 (0.3 –0.8 ) ^[14]
普通感冒	呼吸道飞沫	2–3 ^[15]
水痘	空气传播疾病	10–12^[16]

基本传染数（英语：basic reproduction number、basic reproductive number、basic reproduction ratio、basic reproductive rate；符号为 $R_{0}$ (念为 R nought 或 R zero),^[17]）又称基本再生数，是在流行病学上，指在没有任何防疫作为介入，同时所有人都没有免疫力的情况下，一个感染到某种传染病的初发个案，会把疾病传染给其他多少个人的平均数。基本传染数通常被写成 $R_{0}$ 。 $R_{0}$ 的数字愈大，代表流行病的控制愈难。在没有防疫的情况下，

若 $R_{0}<1$ ，传染病将会逐渐消失。
若 $R_{0}>1$ ，传染病会以指数方式散布，成为流行病（epidemic）。但是一般不会永远持续，因为可能被感染的人口会慢慢减少。部分人口可能死于该传染病，部分则可能病愈后产生免疫力。
若 $R_{0}=1$ ，传染病会变成人口中的地方性流行病。

有效传染数

在研究传染病在人群之中的传播时，通常使用有效传染数（Effective reproduction number）更加方便。有效传染数又称有效再生数，通常被写成 $R_{t}$ ，是估算病毒在一定期间内（t）传播的能力，常用最近7日的确诊个案数来估算；简而言之，有效传染数是在基本传染数的基础上，考虑到防疫措施之后的结果。在实际防疫过程之中，疫情是否可以得到控制，取决于有效传染数是否可以持续小于 1。^[5]

注解

^ 2003年的爆发时的统计则为 0.85，由于该次爆发时实施严格隔离，0.85 只代表该次爆发，而并非病症在不受限制之下的数字。在新加坡案例中，此数字为3。^[6]

参考资料

^ 除特别标注意外，本表中 R₀ 数据来自：History and Epidemiology of Global Smallpox Eradication （页面存档备份，存于互联网档案馆）这份文档来自于 CDC 及 WHO 的一堂有关天花的培训课程（见16 - 17页）。
^ Australian government Department of Health （页面存档备份，存于互联网档案馆） Mumps Laboratory Case Definition (LCD)
^ Brian Gerard Williams; Eleanor Gouws. R0 and the elimination of HIV in Africa. ResearchGate. [2020-06-16].
^ Kretzschmar M, Teunis PF, Pebody RG. Incidence and reproduction numbers of pertussis: estimates from serological and social contact data in five European countries.. PLoS Med. 2010, 7 (6): e1000291. PMC 2889930  . PMID 20585374. doi:10.1371/journal.pmed.1000291.
^ ^5.0 ^5.1 Wallinga J, Teunis P. Different epidemic curves for severe acute respiratory syndrome reveal similar impacts of control measures. Am. J. Epidemiol. 2004, 160 (6): 509–16 [2020-01-25]. PMID 15353409. doi:10.1093/aje/kwh255. （原始内容存档于2007-10-06）.
^ Modeling the SARS epidemic in Hong Kong (ppt) (新闻稿). 香港中文大学. 2003-05-13 [2009-02-02]. （原始内容存档于2014-11-03）（英语）.
^ Mills CE; Robins JM; Lipsitch M. Transmissibility of 1918 pandemic influenza. Nature. 2004, 432 (7019): 904–6. Bibcode:2004Natur.432..904M. PMID 15602562. doi:10.1038/nature03063.
^ Althaus, Christian L. Estimating the Reproduction Number of Ebola Virus (EBOV) During the 2014 Outbreak in West Africa. PLoS Currents. 2014, 6. PMC 4169395  . PMID 25642364. doi:10.1371/currents.outbreaks.91afb5e0f279e7f29e7056095255b288.
^ Read, Jonathan M.; Bridgen, Jessica R.E.; et al. Novel coronavirus 2019-nCoV: early estimation of epidemiological parameters and epidemic predictions. 2020-01-23. doi:10.1101/2020.01.23.20018549.
^ Sanche, Steven; Lin, Yen Ting; Xu, Chonggang; Romero-Severson, Ethan; Hengartner, Nick; Ke, Ruian. Early Release - High Contagiousness and Rapid Spread of Severe Acute Respiratory Syndrome Coronavirus 2 - Volume 26, Number 7—July 2020 - Emerging Infectious Diseases journal - CDC. [2020-06-12]. doi:10.3201/eid2607.200282. （原始内容存档于2020-05-20）（美国英语）.
^ Liu, Ying; Rocklöv, Joacim. The reproductive number of the Delta variant of SARS-CoV-2 is far higher compared to the ancestral SARS-CoV-2 virus. Journal of Travel Medicine. 2021-10-01, 28 (7) [2022-03-26]. ISSN 1708-8305. PMC 8436367  . PMID 34369565. doi:10.1093/jtm/taab124. （原始内容存档于2022-04-19）.
^ Gallagher, James. Covid: Is there a limit to how much worse variants can get?. BBC News. 12 June 2021 [21 July 2021]. （原始内容存档于2021-08-03）.
^ Omicron is the Dominant COVID Variant for Two Reasons. Vitals. 2021-12-28 [2022-03-15]. （原始内容存档于2022-04-21）（美国英语）.
^ Kucharski AJ, Althaus CL. The role of superspreading in Middle East respiratory syndrome coronavirus (MERS-CoV) transmission. Euro Surveillance. June 2015, 20 (25): 14–8. PMID 26132768. doi:10.2807/1560-7917.ES2015.20.25.21167  .
^ Freeman C. Magic formula that will determine whether Ebola is beaten . The Telegraph. Telegraph.Co.Uk. [30 March 2020]. （原始内容存档于January 12, 2022）.
^ Ireland's Health Services. Health Care Worker Information (PDF). [2020-03-27]. （原始内容 (PDF)存档于2020-03-26）.
^ Milligan GN, Barrett AD. Vaccinology : an essential guide. Chichester, West Sussex: Wiley Blackwell. 2015: 310. ISBN 978-1-118-63652-7. OCLC 881386962.

延伸阅读

Scholia上有关基本传染数（Q901464）的信息

Heesterbeek JA. A brief history of R0 and a recipe for its calculation. Acta Biotheoretica. 2002, 50 (3): 189–204. PMID 12211331. S2CID 10178944. doi:10.1023/A:1016599411804. hdl:1874/383700.
Heffernan JM, Smith RJ, Wahl LM. Perspectives on the basic reproductive ratio. Journal of the Royal Society, Interface. September 2005, 2 (4): 281–93. PMC 1578275  . PMID 16849186. doi:10.1098/rsif.2005.0042.
Jones JH. Notes on $R_{0}$ (PDF). 1 May 2007 [6 November 2018]. （原始内容存档 (PDF)于2014-09-12）.
Van Den Driessche P, Watmough J. Further Notes on the Basic Reproduction Number. Mathematical Epidemiology. Lecture Notes in Mathematics 1945. 2008: 159–178. ISBN 978-3-540-78910-9. doi:10.1007/978-3-540-78911-6_6.

参见

流行病学隔间模型（英语：Compartmental models in epidemiology）

外部链接

What Is R0? Gauging Contagious Infections. [2021-07-25]. （原始内容存档于2020-05-26）.

[7] 2003年的爆发时的统计则为 0.85，由于该次爆发时实施严格隔离，0.85 只代表该次爆发，而并非病症在不受限制之下的数字。在新加坡案例中，此数字为3。^[6]

[Smallpox-1] 除特别标注意外，本表中 R₀ 数据来自：History and Epidemiology of Global Smallpox Eradication （页面存档备份，存于互联网档案馆）这份文档来自于 CDC 及 WHO 的一堂有关天花的培训课程（见16 - 17页）。

[2] Australian government Department of Health （页面存档备份，存于互联网档案馆） Mumps Laboratory Case Definition (LCD)

[3] Brian Gerard Williams; Eleanor Gouws. R0 and the elimination of HIV in Africa. ResearchGate. [2020-06-16].

[4] Kretzschmar M, Teunis PF, Pebody RG. Incidence and reproduction numbers of pertussis: estimates from serological and social contact data in five European countries.. PLoS Med. 2010, 7 (6): e1000291. PMC 2889930  . PMID 20585374. doi:10.1371/journal.pmed.1000291.

[sars1-5] 5.0 ^5.1 Wallinga J, Teunis P. Different epidemic curves for severe acute respiratory syndrome reveal similar impacts of control measures. Am. J. Epidemiol. 2004, 160 (6): 509–16 [2020-01-25]. PMID 15353409. doi:10.1093/aje/kwh255. （原始内容存档于2007-10-06）.

[6] Modeling the SARS epidemic in Hong Kong (ppt) (新闻稿). 香港中文大学. 2003-05-13 [2009-02-02]. （原始内容存档于2014-11-03）（英语）.

[8] Mills CE; Robins JM; Lipsitch M. Transmissibility of 1918 pandemic influenza. Nature. 2004, 432 (7019): 904–6. Bibcode:2004Natur.432..904M. PMID 15602562. doi:10.1038/nature03063.

[9] Althaus, Christian L. Estimating the Reproduction Number of Ebola Virus (EBOV) During the 2014 Outbreak in West Africa. PLoS Currents. 2014, 6. PMC 4169395  . PMID 25642364. doi:10.1371/currents.outbreaks.91afb5e0f279e7f29e7056095255b288.

[10] Read, Jonathan M.; Bridgen, Jessica R.E.; et al. Novel coronavirus 2019-nCoV: early estimation of epidemiological parameters and epidemic predictions. 2020-01-23. doi:10.1101/2020.01.23.20018549.

[11] Sanche, Steven; Lin, Yen Ting; Xu, Chonggang; Romero-Severson, Ethan; Hengartner, Nick; Ke, Ruian. Early Release - High Contagiousness and Rapid Spread of Severe Acute Respiratory Syndrome Coronavirus 2 - Volume 26, Number 7—July 2020 - Emerging Infectious Diseases journal - CDC. [2020-06-12]. doi:10.3201/eid2607.200282. （原始内容存档于2020-05-20）（美国英语）.

[12] Liu, Ying; Rocklöv, Joacim. The reproductive number of the Delta variant of SARS-CoV-2 is far higher compared to the ancestral SARS-CoV-2 virus. Journal of Travel Medicine. 2021-10-01, 28 (7) [2022-03-26]. ISSN 1708-8305. PMC 8436367  . PMID 34369565. doi:10.1093/jtm/taab124. （原始内容存档于2022-04-19）.

[bbc-sarscov2-variants-13] Gallagher, James. Covid: Is there a limit to how much worse variants can get?. BBC News. 12 June 2021 [21 July 2021]. （原始内容存档于2021-08-03）.

[14] Omicron is the Dominant COVID Variant for Two Reasons. Vitals. 2021-12-28 [2022-03-15]. （原始内容存档于2022-04-21）（美国英语）.

[15] Kucharski AJ, Althaus CL. The role of superspreading in Middle East respiratory syndrome coronavirus (MERS-CoV) transmission. Euro Surveillance. June 2015, 20 (25): 14–8. PMID 26132768. doi:10.2807/1560-7917.ES2015.20.25.21167  .

[Telegraph_Ebola-16] Freeman C. Magic formula that will determine whether Ebola is beaten . The Telegraph. Telegraph.Co.Uk. [30 March 2020]. （原始内容存档于January 12, 2022）.

[17] Ireland's Health Services. Health Care Worker Information (PDF). [2020-03-27]. （原始内容 (PDF)存档于2020-03-26）.

[18] Milligan GN, Barrett AD. Vaccinology : an essential guide. Chichester, West Sussex: Wiley Blackwell. 2015: 310. ISBN 978-1-118-63652-7. OCLC 881386962.

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