16Zika virus (ZIKV) is an emerging flavivirus typically causing a dengue-like febrile illness, but 17 neurological complications, such as microcephaly in newborns, have potentially been linked to 18 this viral infection. We established a panel of in vitro assays to allow the identification of ZIKV 19 inhibitors and demonstrate that the viral polymerase inhibitor 7-deaza-2'-C-methyladenosine 20 (7DMA) efficiently inhibits replication. Infection of AG129 (IFN-α/β and IFN-γ receptor knock-21 out) mice with ZIKV resulted in acute neutrophilic encephalitis with viral antigens accumulating 22 in neurons of the brain and spinal cord. Additionally, high levels of viral RNA were detected in 23 the spleen, liver and kidney, and levels of IFN-γ and IL-18 were systematically increased in 24 serum of ZIKV-infected mice. Interestingly, the virus was also detected in testicles of infected 25 mice. In line with its in vitro anti-ZIKV activity, 7DMA reduced viremia and delayed virus-26 induced morbidity and mortality in infected mice, which also validates this small animal model 27 to assess the in vivo efficacy of novel ZIKV inhibitors. Since AG129 mice can generate an 28 antibody response, and have been used in dengue vaccine studies, the model can also be used to 29 assess the efficacy of ZIKV vaccines. 30 31 Article Summary Line: A robust cell-based antiviral assay was developed that allows to screen 32 for and validate novel inhibitors of Zika virus (ZIKV) replication. The viral polymerase inhibitor 33 7-deaza-2'-C-methyladenosine (7DMA) was identified as a potent ZIKV inhibitor. A mouse 34 model for ZIKV infections, which was validated for antiviral studies, demonstrated that 7DMA 35 markedly delays virus-induced disease in this model.36 37