IFNB1 and infection: The data is consistent with a model where H5N1-NS1 103F+106M virus infects the bronchiolar epithelium in the lung but induced inhibitory level of IFN that prevented alveolar infection and limited peak titers to 105 pfu/g in contrast to the 103L+106I variant that produced 108 pfu/g at 3 dpi in the lung due to the spread of infection to the alveoli in the presence of the same levels of IFN-β at 1 and 3 dpi (Figure 2).