Influence of asymptomatic infections for the effectiveness of facemasks during pandemic influenza

In this paper, the SEIR model is generalized by introducing an asymptomatic class to quantify the influence of wearing N95 facemasks in reducing the spread of influenza H1N1. What´s more, we explain the control reproduction number Rc according to the biological meaning reasonably. Without any intervention, the basic reproduction number R0=1.83 and there will be a large outbreak of infectious diseases. If N95 facemasks are 50% effective in reducing susceptibility and infectivity, 50% of population wear them on the first day, the basic reproduction number will be decreased from 1.83 to 1.17 and the final size reduced from 73% to 2%.