Found a few more paper related to occult in looking around the net:
"Recurrence of hepatitis C virus during leucocytopenia and spontaneous clearance after recovery from cytopenia: a case report. (12/07)"
"Occult hepatitis C and B virus infections in hepatocellular carcinoma. (1/07)"
"Presence of multiple genotype-specific antibodies in patients with persistent infection with hepatitis C virus (HCV) of a single genotype: evidence for transient or occult superinfection with HCV of different genotypes. (8/99)"
TnHepGuy