IFNAR1 and infection: Mouse models have been developed using YFV 17D including (i) infection of AG129 mice resulting in neurotropic disease [26] and (ii) infection of young (3–4 week old) IFNAR-/- mice showing viscerotropic and neurotropic disease [27], although Meier et al., reported no pathology in 3–4 week old A129 mice infected with YFV 17D-204 [28].