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Basic reproduction number

In epidemiology, the basic reproduction number (sometimes called basic reproductive rate) of an infection is the mean number of secondary cases a typical single infected case will cause in a population with no immunity to the disease in the absence of interventions to control the infection. It is often denoted R0. This metric is useful because it helps determine whether or not an infectious disease will spread through a population. It was originally used by George MacDonald in 1952, who constructed population models of the spread of malaria.

Values of R0 of well-known infectious diseases[1]
DiseaseTransmission R0
HIV/AIDS Sexual contact2-5[2]
Diphtheria Saliva 6-7
(1918 pandemic strain)
Airborne droplet 2-3[3]
Measles Airborne 12-18
Mumps Airborne droplet 4-7
Pertussis Airborne droplet 12-17
Polio Fecal-oral route 5-7
Rubella Airborne droplet 5-7
SARS Airborne droplet2-5[4]
Smallpox Social contact6-7


R0 < 1

the infection will die out in the long run (provided infection rates are constant). But if

R0 > 1

the infection will be able to spread in a population. Large values of R0 may indicate the possibility of a major epidemic.

Generally, the larger the value of R0, the harder it is to control the epidemic. In particular, the proportion of the population that needs to be vaccinated to provide herd immunity and prevent sustained spread of the infection is given by 1-1/R0. The basic reproductive rate is affected by several factors including the duration of infectivity of affected patients, the infectiousness of the organism, and the number of susceptible people in the population that the affected patients are in contact with.

Other uses

R0 is also used as a measure of individual reproductive success in population ecology[5], evolutionary invasion analysis and life history theory.


  1. ^ Unless noted R0 values are from: History and Epidemiology of Global Smallpox Eradication From the training course titled "Smallpox: Disease, Prevention, and Intervention". The CDC and the World Health Organization. Slide 16-17.
  2. ^ Anderson RM, May RM (1979). "Population biology of infectious diseases: Part I". Nature 280 (5721): 361-7. PMID 460412.
  3. ^ Mills CE, Robins JM, Lipsitch M (2004). "Transmissibility of 1918 pandemic influenza". Nature 432 (7019): 904-6. doi:10.1038/nature03063. PMID 15602562.
  4. ^ Wallinga J, Teunis P (2004). "Different epidemic curves for severe acute respiratory syndrome reveal similar impacts of control measures". Am. J. Epidemiol. 160 (6): 509-16. doi:10.1093/aje/kwh255. PMID 15353409.
  5. ^ de Boer, Rob J. Theoretical Biology. Retrieved on 2007-11-13. 
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Basic_reproduction_number". A list of authors is available in Wikipedia.
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