IFNA1 and infection: However, although flaviviruses can inhibit IFN-induced responses, type I IFN still restricts viral replication in vitro, but only when added prior to infection, since it is much less effective once the infection is established (Diamond et al., 2000; Anderson and Rahal, 2002; Crance et al., 2003; Lin et al., 2004; Ho et al., 2005; Samuel and Diamond, 2005).