Which of the following explanations account(s) for the fact that hepatitis C is the most common cause of posttransfusion hepatitis?

The ability to specifically identify persons infected with HCV has only recently become available. Therefore, data about epidemiology are less than complete. It is very likely not true that more blood donors carry HCV because of the large preponderance of HBV in the United States. It is true, however, that successful elimination of most of the HBV carriers occurs through routine testing. Although serologic tests are available for HCV, they are tests, not of antigen, but of antibody. Therefore, this test alone may not screen out persons who are infected but have not yet developed or may never develop antibody. Risk groups for the relatively newly defined HCV may well not be comprehensively established, and therefore this explanation may be a contributor. There are no differences in virulence between these classes of hepatitis virus.