3.2.1. Basic reproduction number. The basic reproduction number R 0 is an indicator that is often used to measure the transmissibility of a pandemic outbreak. Simply put, it is the average number of other individuals each infected person will infect in a completely susceptible population. Analyses of previous influenza pandemics estimated R 0 for large communities to lie between 1.2 and 3 (Mills et al. 2004; White & Pagano 2008) . For the recent H1N1 pandemic, some early studies have suggested R 0 to range between 1.4 and 1.6 (Fraser et al. 2009 )-indicating relatively low transmissibility-while others estimated it to be as high as 3.1 in certain countries such as Mexico (Boglle et al. 2009 ).