IL6 and infection: These results suggest that the MA-H3N2 mutations may enhance the ability of the virus to replicate in mouse lungs, which is positively correlated with weight loss and high lungs viral titers at day 6 p.i. High levels of IL-6 have been observed to correlate with infection severity while IL-5 levels were associated with a delay in influenza virus clearance in infected mice49–51.