With the exception of CXCL10 (IP10) and interferon-stimulated gene 20 kDa protein (ISG20), both of which are dually regulated by IFN-α/β and IFN-γ, low-level ISG induction is restricted to the first weeks of infection and subsides before peak HAV RNA abundance in the liver (Lanford et al., 2011). Here, ISG20 is linked to infection.