User blog comment:Argorrath/Treyarch posts a message of zombies; possibly hinting to a DLC 4/@comment-213.107.179.220-20130801100329

I would just like to point out that the zombies storyline has always just sort of thrown explanations together to create the setting of certain maps so it could be entirely possible that during the experiments on the other 3 they somehow stopped ageing or something like that.

To me it definitely sounds like an origin story ('The Doctor' always being used with Richtofen, Nikolai being outcast, Takeo mentioning honour, stereotypical american speech for Dempsey eg Fritz). This would however mess with the existing explanation of Nacht and Verrukt as that is meant to be Dempsey's origin story (assuming Richtofen captures them at the end of this origin story).

Furthermore, I still believe that 'Doctor' is a red herring as Maxis is also a doctor, this is before Richtofen goes insane and the other three pages are from the rest of the Original Crew. On the other hand Maxis is well known for his diary entries though I would expect his to be the overall description of the map or introduction message when you load up zombies.

Finally, can anyone work something out to do with the dates? My guess would be that it is set in January 1918 as each page advances a month. Wikipedia also states that this is when Spanish Flu broke out so make of that what you will