Effective reproduction number. The effective reproduction number < unc determines the average number of secondary cases resulting from one typical infectious individual during the infectious period without the implementation of facemasks. Since there is a delay in the implementation of facemasks the initial growth of the epidemic is affected by < unc . The estimates of < unc for pandemic (H1N1) 2009 vary widely, the common range is assumed to be between 1.2 and 2.2. As the value of < unc increases the number of pandemic (H1N1) 2009 cases increases significantly as shown graphically in Figure 4 .