sentence: CrAssphage , PMMoV and AdV and PyV are usually present up to 4 log higher concentrations in seawater than hepatitis A virus , norovirus and sapovirus ( Dias et al ., 2018a , Dias et al ., 2018b ; Farkas et al ., 2018 ; Fongaro et al ., 2015 ; Moresco et al ., 2012 ; Rusi ñ ol et al ., 2015 ; Symonds et al ., 2018 ) , however , one study found that the concentration of indicators and norovirus GII , rotavirus and sapovirus were similar , approx .