Very good responses guys - we're getting so good at this!
Well.........you are anyways :)
jdwithhcv explained it simply and clearly. At some point during treatment, one hopes you become undetectable. Otherwise they will stop treatment. But that doesn't mean the virus is actually gone. It only means it is not detected in your bloodstream. You continue treatment for months after you become undetectable to sweep up any remaining virus lurking in your liver and pancreas.
When you stop treatment, one of two things happen: the few lurking strands of virus re-emerge and multiply and the virus quickly becomes detectable again. Or the virus does not re-emerge. If your blood tests are clear for six months you are said to have achieved a Sustained Viral Response. The changes of the virus emerging after that point are very slight.
About 50% of patients with genotype 1 who treat for 48 weeks achieve SVR.
SVR is sustained virological response. This is achieved when the patient successfully clears the virus, and PCR test result is still UND six months after completing treatment.