This is such a captivating story! I've been reading it straight through, but Harry's pneumonia made me recall something: His lowered immune system and the need for avoiding germs seems at odds with Floo travel, and an earlier chapter even mentioned Harry shaking off soot after traveling via Floo. I don't know if the soot plays any role in his condition, but I agree it's difficult to avoid contamination with other people coming and going. It'll be interesting to see what Severus comes up with to counter it ...
Author's Response: Thank you! I'm glad you're enjoying the journey!
Yes, the floo would absolutely be an issue, but I purposely decided to ignore it in this fic since another "cancer Harry" story has that as a major point in it. That author did a really great job with handling Harry's autoimmunity and I didn't feel comfortable crossing over too much there.