Influenza is one of respiratory infections causing the highest morbidity and mortality rates. Every day tens of millions of people suffer from virus infection worldwide with varying severity and with a high economic impact. Influenza transmission from person to person occurs in various ways. This study is an attempt to understand airborne transmission in indoor locations by examining the relation between environmental parameters such as temperature and relative humidity with the number of influenza like illness (ILI) cases. It is proposed that the pattern of influenza activity is primarily a function of indoor relative humidity in temperate regions. This conclusion is based on previous virus viability experiments and on our observation of a strong correlation between influenza like illness cases and indoor relative humidity. Historical data reveals that the peak in influenza like illness cases occurs when the indoor relative humidity is around 10-30%. This study also focuses on the aerosol mode of transmission via expelled particles of human cough. Experiments were carried out for concentration measurements at various locations of cough particles in an Environmental Chamber (EC) at a Morgantown NIOSH facility. A simulated cough machine capable of replicating human cough in real time flow and particle size distribution was used for the aerosol injection. A computational fluid dynamics (CFD) model was developed to simulate the human cough in a modeled room. The results of experiments and simulations are compared to assess the suitability and accuracy of CFD simulation for such flow. The last step in this study is to evaluate the potential of inhalation of dispersed cough droplets in room by breathing. Since the primary mechanism of infection transmission is believed to be via inhalation of virus laden droplets, a theoretical study was conducted to define the sphere of influence of human breathing.