The hepatitis C virus (HCV) antibody test identifies whether you were exposed to HCV at some point in your life, whereas the viral load detects the actual virus. Approximately 15 to 25 percent of people who are exposed to hep C are able to clear the virus on their own, resulting in a nondetectable viral load. If the viral load is nondetectable, then you don’t have hep C and you can’t infect anyone else.
One way to think about it is to compare the antibody test to a photograph. A photo of you standing next to a famous person proves that you encountered that person. However, the only way to know if that famous person is standing next to you now is to look. The viral load test actually looks, whereas the antibody test indicates a past encounter.