Bacteria and viruses should require only micro-currents to destroy them or render them harmless. Can such an approach be used to sterilize water...or perhaps even blood (en-vitro or even en-vivo)?
Purifying water with an electric filter has been investigated:
http://web.stanford.edu/group/knowledgebase/cgi-bin/2010/09/02/purifying-water-by-electrocuting-pathogens/
I'm not sure why this would be any better than standard UV and 0.2um filters but perhaps it might turn out cheaper or more convenient in some circumstances. In terms of medical use it's not going to have any use trying to kill pathogens inside the body. Simply because this type of thing would kill healthy tissue as well.