As secretion of type I interferon (IFN) is a classical indication of immune activation upon viral infection [53], we first infected mouse embryonic fibroblasts (MEFs) with IIV-6 or DCV and investigated the induction of IFN-β and tumor necrosis factor α (TNF-α) as markers for an early innate immune antiviral response in infected cells. Here, TNF is linked to viral infectious disease.