ABSTRACT
Viruses were so named after the Latin for poison. Among the various descriptives used to
characterize viruses, “filterable” was a key attribute. Over the past three decades, there
have been phenomenal advances in membrane filtration technologies that have allowed
development of membranes that retain viruses by a mostly size-exclusion based
mechanism. Size-based (predominantly) filtration-removal of viruses is similar to
removal of other viable or non viable particulates (and several chapters in this book have
been dedicated to its discussion). The challenge lies in the fact that many therapeutic
proteins, either native or recombinant, are at the size limit of small viruses; consequently,
membrane filtration for virus removal must remove viruses of concern without
significantly compromising product yield.