STAT1 and infection: We chose to generate hematopoietic cell-specific STAT1 KO mice because a previous study from our group determined that these mice were hypersusceptible to infection with other orthoflaviviruses, such as yellow fever virus strain 17D, and we hypothesized that YFV and USUV may have a similar reliance on STAT1-mediated signaling in hematopoietic cells [60].