This answered most of the questions: http://www.wjgnet.com/1007-9327/12/6922.asp
Occult hepatitis C virus infection: A new form of hepatitis
Abstract
Occult hepatitis C virus (HCV) infection is a new recently characterized entity. This occult infection can be present in two different clinical situations: in anti-HCV negative, serum HCV-RNA negative patients with abnormal liver function tests and in anti-HCV positive subjects with normal values of liver enzymes and without serum HCV-RNA. This review describes recent studies of occult HCV infection in both kinds of patients.
CHRONIC VERSUS OCCULT HEPATITIS C
Once occult HCV infection is identified, one important question is if the clinical characteristics of this infection differ from those usually found in chronic hepatitis C. Trying to answer this question, the biochemical, virological and histological features of a group of 68 patients with occult HCV infection were compared with those of a group of 69 patients with histologically proven chronic hepatitis C[14]. Groups were matched with respect to gender, age and known time duration of the disease. Triglycerides and cholesterol values were significantly higher in occult HCV infection, while alanine aminotransferase, gammaglobulin, alpha-fetoprotein and iron levels were significantly higher in patients with chronic hepatitis C. The number of patients who had necroinflammatory activity and fibrosis in the liver biopsy was significantly higher in the group with chronic hepatitis C than in the group with occult HCV infection, but no difference was found in the percentage of patients with liver steatosis between both groups. Finally, as could be expected, the percentage of HCV-infected hepatocytes (determined by in situ hybridization) was significantly lower in patients with occult HCV. Thus, it was concluded that occult HCV infection is a milder disease, with less liver damage than chronic hepatitis C. Nevertheless, as patients with occult hepatitis C may present dyslipidemic disorders, studies on the natural history of occult HCV infection should be performed to prove the role of occult HCV as the cause for liver injury in these patients.
The term "occult" used here means "hidden", and in the sense used here it is describing any Hep C that remains below current blood test detectability levels (i.e. - "hidden").
If you go over to the Health Page here at MedHelp that is dedicated to Occult Hep C, the following two papers should give you a pretty good definition and overview:
"Occult Hepatitis C virus persistence: identification and characteristics.[PDF] (2/06)"
and
"Occult hepatitis C virus infection: A new form of hepatitis C. (11/06)"
TnHepGuy