STAT1 and infection: Regardless of the dose, all Ifnar1-/- and Stat1-/- mice experienced incremental weight loss, increasing clinical signs, and ultimately succumbed to lethal infection between 5–6 dpi and 6–8 dpi, respectively (Fig 3A–3F), in sharp contrast to wild-type mice of which 100% survived infection with 103 FFU of USUV.