lets recap a little bit here... (away from books so going off memory, help me out here guys!)
Sometime back in 2071 Fastjack and a select team raid a data store that is off the grid... Fastjack feels that this event is ground zero.
Plan 9 gets infected, and almost immediately is consumed by the invading personality, forcing Plan-9 to betray contacts that lead them to their capture and/or death
Lanier is also infected, but in this case the spread of the invading "thing" seems slower... more deliberate.. almost as if it is taking it's time or trying to hide?
Fastjack is infected, yet the rate if infection takes almost 2/3 years to overcome him... or at least get to the point that he feels he is losing and needs to remove himself.
A trio of mages, seemingly under the effects of whatever this is, blow themselves, and their guests up in a deliberate magical attack by one of the infected... and the conversation leads us to believe that they know EVERY skill and ability of their hosts... if not fully control it all the time (one of them mentions "losing" the spell ability for a moment in the bedroom conversation)
Gargin base goes dark for 130 days... the crew is changed.. more aggressive, confused...
The underwater base are even more aggressive and disturbed....
Dietrich comes back with what looks like on the surface as full blown MPD (if you can get 3 psycologists to agree that MPD exists!)
So, if Fastjack is correct on "ground zero" then we have "something" that has spread across the world and into space in 2 years, and infected hundreds....
After 2 years, the method and mode of infection is impossible to trace (is it spread by a handshake? bodily fluids? only over the matrix? DNI connections, infected nanobots....
****
Did I miss anything?
IMO, I think the transmission method is the Matrix, and I think this also explains the Gargin, Mars and underwater colonies and their random, odd behavior (even for the "invaded?")
These 3 locations would not have the constant background of the matrix humming in their "ear" all the time....
Water a depth, has massive weight (32feet of water = 1 atmosphere, or 14.7 pounds of pressure....depending on the depth of the habitant.... that could be massive! if it was at 1500 feet below sea level, that would be 46.875 Atm of pressure... or almost 700 pounds of pressure!) I highly doubt that a standard matrix signal could reach that far down.... Mostly likely they have a high intensity transmitter and use it to do burst transmissions. The same thing for both the Mars base and Gargarin base.... (except in those cases it is distance)
So, I think, whatever we are dealing with used these burst transmissions to get into and infect the inhabitants.
The only thing don't know is "Why?" Are these random infections or are these targeted. If there are targeted, why these people? Why not higher up the pecking list? Why Lanier and not Villiers? or Knight himself?