However, two in vivo mouse studies suggest IFN-γ may not play a significant role in control of the infection; one study demonstrated similar levels of viremia and mortality in EEEV-infected IFN-γ deficient mice compared to wild-type mice while another demonstrated IFN-γ played only a minor role in extending of the average survival time (Aguilar et al., 2005; Gardner et al., 2009). This evidence concerns the gene IFNG and infection.