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Basic reproduction number
From Wikipedia, the free encyclopedia
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.
| Disease | Transmission | R0 |
|---|---|---|
| HIV/AIDS | Sexual contact | 2-5[2] |
| Diphtheria | Saliva | 6-7 |
| Influenza (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 droplet | 2-5[4] |
| Smallpox | Social contact | 6-7 |
When
- 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.
R0 is also used as a measure of individual reproductive success in population ecology[5], evolutionary invasion analysis and life history theory.
- ^ 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.
- ^ Anderson RM, May RM (1979). "Population biology of infectious diseases: Part I". Nature 280 (5721): 361-7. PMID 460412.
- ^ Mills CE, Robins JM, Lipsitch M (2004). "Transmissibility of 1918 pandemic influenza". Nature 432 (7019): 904-6. doi:10.1038/nature03063. PMID 15602562.
- ^ 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.
- ^ de Boer, Rob J. Theoretical Biology. Retrieved on 2007-11-13.