I think Hunter is a red herring, so to speak. I think it's stated in the summary for PLAGUE that it's spread by bugs anyway (or the bugs accompany it, idk). But, I digress.
My theories (related to the plague illness and the series in general):
- The plague illness is something to do with Emily & Brother at the farm house place (seriously, I thought they were gonna have a way bigger part and then they just sorta weren't mentioned ever again for the whole book. xD).
- Sanjit replaces whatever major character dies in PLAGUE/DARKNESS (I can't remember which book MG has stated he'll kill a main-ish character off in). Or he kills that main character.
- Drake and Astrid have another run-in. They're both (I think?) on the cover of PLAGUE so. (on that note; Astrid needs to get the heck of the covers. I want Edilio and Dekka on there.)
- Quinn needs to have a proper part in the next few books because he was barely in LIES and then when he was he was a complete jerk.
- Howard and Orc will definately have bigger parts because they're firmly in the "good books" now.
- the FAYZ wall disappearing for a second at the end of LIES was an illusion by the Gaiaphage (c'mon, what're the chances that the visions Nerezza/the Gaiaphage was giving Orsay and what could be outside the FAYZ (if anything) are the same/true?).
- Zil will be possessed by the Gaiaphage or something.
-Lana will kill herself, become the Crazy Dog Lady of the FAYZ, get repossessed by the Gaiaphage or just not really reappear until DARKNESS or LIGHT. (I like her, so she can't die. xD;)
And this series is awesome. Not perfect (no book is ;c) but still very, very good. <3
[nobody else has spoiler tag'd their posts so I haven't done so to mine. Mods please do correct me if I need to~]