Figure 6.7 Effective and basic reproduction numbers for Spanish influenza, 1918. Morbidity data from cities in Europe and America for community-based and confined settings. Several different methods based on the growth rate and final size of the epidemic have been used to estimate the effective and basic reproduction numbers for the 1918 (Spanish) influenza virus. The effective reproduction number (the average number of secondary infectious cases produced by a typical infectious case in a given population) for the 1918 influenza virus was in the range 1.2–3.0 and 2.1–7.5 for community-based and confined settings, respectively. The basic reproduction number (the average number of secondary infectious cases resulting from a typical infectious case in a totally susceptible population) was in the range 2.4–4.3 and 2.6–10.6 cases in community-based and confined settings, respectively.

Source: Reproduced from Vynnycky et al, Estimates of the reproduction numbers of Spanish influenza using morbidity data, International Journal of Epidemiology, Volume 36, Issue 4, pp. 881-9, Copyright © 2007 International Epidemiological Association, by permission of Oxford University Press.