Thus lethal pathology at these doses may have been a function of extensive tissue infection (Figure 2 and 3) and high cytokine induction to induce hypercytokinemia of IFN-β that approximated the mouse LD50 intramuscular dose for type I IFN of 1,300 pg/g [77] indicating that these mice possessed toxic levels of IFN-β, that may contribute to the lethality associated with the 103L+106I induced pneumonia (Figures 1, 2 and 3). This evidence concerns the gene IFNB1 and susceptibility to pneumonia measurement.