F2 and hepatitis A virus infection: Japanese studies suggest that HEV-4 infections are associated with more severe hepatitis, higher peak aminotransferase activities (Mizuo et al., 2005; Ohnishi et al., 2006; Murata et al., 2019), shorter prothrombin times (Mizuo et al., 2005; Ohnishi et al., 2006; Murata et al., 2019) and higher total bilirubin concentrations (Mizuo et al., 2005; Murata et al., 2019).