AVIAN INFLUENZA, DRAWING,Comparison of the regions of the organism infected by the human influenza virus and the avian influenza virus. Human influenza virus is mainly present in the upper respiratory system : nasal mucosa, sinus, pharynx, trachea and main bronchi (in green). It can therefore be easily transmitted to the family circle, via droplets of the cough. The avian influenza virus (H5N1) colonizes preferentially the deepness of the lung : bronchioles and pulmonary alveoles (in blue). It is therefore little contagious, because it does not remonte sufficiently into the respiratory system to be emitted by the cough.