Complex sentence: The former is a method in which all of the viruses are simply extricated from the sample completely and the latter method is one in which the viruses may remain in the final product, but in a non-infective form.
Split into simpler sentences: The former is a method in which all viruses are simply extricated from the sample completely. The latter method is one in which the viruses may "remain" in the final product, but in a non-infective form.