Okay, so it's confirmed Nana can only sense Diclonius that are in "postal" mode, since Mariko reverted to her "of age" mentality.
Kurama envision of Mariko as her age progressed is so heartbreaking
I'm not sure blowing up the virus would succeed, detonation will damage most if not all pathogen, not release freely to the atmosphere. Weather baloons would be more efficient and since they can travel in the jetstream, spread the infection on much greater scale...