In summary, our experiments have provided the first analysis of the 3D structure of tick-borne flavivirus infection in both mammalian and arthropod host cell systems. We observed vesicles with pores connecting to other vesicles or opening to the cytosol in tick-borne flavivirus infection, similar to those seen in mosquito-borne flavivirus infection. We have shown for the first time the 3D ultrastructure of acutely and persistently, flavivirusinfected arthropod cells, facilitating the observation of the shift that occurs from round vesicles during acute TBFV-infection to the elongated tubules that dominate persistent infection. Future experiments are needed to better understand the increasing presence of tubules at the site of membrane rearrangement during persistent infection. 