Viral Clearance SAL 10-6 With Single Sterilization Technique

For common sterilization techniques (autoclave, EtOH), it is accepted that these are terminal sterilizations that also reduce viral load. I am curious, if you cannot produce a viral titer greater than 10^6, how would you prove that these methods (or any method) provide terminal sterilization to this level? Thanks for any help!

Best,
Mike