I remember reading it in some science magazine (PopSci, PopMech, SciAM, I don't remember), that proposed the terraforming of Venus (or was it Mars?) by seeding it's atmosphere with bacteria of some sort. Theeywould be delivered via reusable missile payload/spaceplane thingamabobs taht would dip into the upper atmosphere, release their payloads, and fly back to Earth. Seeing your story makes me think, that if there was eer a global pandemic on the scale here in this story, then surely some similar means could be used to spread a cure, via some anti-bac or sterile virus. Of course, the opposite also remains true, for what would surely be a possibly more frightenning alternative to nukes in "mutually assured destruction" An idea afor your story, perhaps?