+ + + + Edited on 27th August 2012; thank you Litmaster for your advice + + + +
To cut things short let me put the baseline-theory upfront; the explanation would follow on the Wall of Words ahead, but you wouldn't have to read it all, if you are just interested in the essence of it at all; the theories cover all my postings within this thread. When you risk reading the wall of words, please keep in mind that the first Wall of Word was written before I learned about season 3 ...
Theory 1: Zombie-ism might be connected to the blood-type of the victims. This would explain a couple of things:
a) Slow-Turners and None-Turners having had some exchange with zombified blood or tissue.
b) The rather small amout of Zombies compared to the average number of inhabitants and visitors of L.A.
c) Different kinds of Zeds show up which have very different qualities. There are the huge masses, but there are few special ones.
Theory 2: Evil-gene theory - Zombieism progresses in a body as soon as the number of "evil genes" is high enough - genes that may be the source of violence, lying, deceiving and whatnot. This would explain some things as well:
a) The more evil Zeds were in their life as humans, the more powerful they are as Zeds (Behemoths, smart ones, "Ink").
b) The rather small amount of Zeds after very few days in L.A. with a nearly completely deserted city which normally holds more then 3.6 Million people ...
Theory 2 is covered in a later posting, not in the following wall of words.
All the best!
+ + + + Edit ends + + + +
+ + + + WALL OF WORDS AHEAD + + + +
I have run through many of the topics in this subsection of this forum. And I have learned a lot about different ways Zed-ism is established - from mutations, radiation, intended or misguided experiments, viruses, nanobots or even demonic influences we had many different approaches and suggestions. And many to most of them were backed with "facts" from the WA-series or proven based on more or less common to uncommon standard-Zed-ism-theories. (I was so glad to read something which reminded me of the theories in the movie of "Doom" ... ).
Ok, still I am not so much convinced about any of the theories - not even by the stronger theories. Because not one of the ideas considers the survivors or the people who survived at least until they were eaten or used for some sinister rituals of whatever kind. The leading question here is: Why did ("only so few?") people did not end up as 'Zombies'? What makes them different from the masses who "almost instantly" or at least in a very short time turned from human beings to "something else"?
All of the theories discussed in this forum-section focus on the Zeds and the reason why actually they are Zeds. While the one half of theories is about some global thing happening, the other part is about an experiment on few gone wild. But not one of the theories considers the spreading of the disease and why actually the spreading seem to have some limitations to it. So, in the following paragraphs I will throw in some ideas. This might be kind of confusing at times, because it is actually a stream-of-consciousness-technique-based attempt borderlining brainstorming; but I try hard to follow kind of a red line ... Enjoy!
Please keep in mind that I have just listened to the seasons #1 and #2 so far; therefore I was not able to take important information from season #3 into consideration.
Amendment #1: I kept going with listening and will add some changes on subsequent postings in order to prevent confusion between the original posting and replies.
1. When it all began
I would like to focus on season 1 for a bit, because compared to what we learn about Zeds in season 2 (3 I have not yet listened to) season 1 is the source to rely on.
In the very first episode the audience learns about Michael being called in order to get to work, because some serious shit is happening.
Just a bit later he is caught in a traffic jam - very likely caused by panicking people wishing to flee the place -, and Michael witnesses an attack from a Zed against another civilian in his car, because he made so much noise.
More or less all of a sudden hell breaks loose. Michael, Saul and more find shelter and thus prevent getting devoured or captured by the hordes of Zeds.
It is obvious that the number of Zeds is not so big at the beginning, but big enough that their initial "attack" (for now I treat it as an attack) occurs suddenly and strong enough that even military forces are called in to deal with it. In the very beginning of episode 1 there is no general alarm or generally tense situation about riots or mysterious cases of people freaking out. Literally suddenly news start to spread about attacks in many places, and almost instantly Michael and others are called to arms. As the audience learns later news from different parts seem to follow or cover a similar pattern, until all of a sudden all broadcasting stations stop broadcasting.
In other words: There needs to be kind of an initial swarm of attackers, which is btw supported by the reports of different survivors. Michael marks all this on a map of L.A. and pinpoints the starting point around "ground zero". And this is probably what has happened in other cities as well.
Within the first episode of the show the audiences learns more about the spreading: Most inhabitants of L.A. are nearly extinguished within hours, while the amount of Zeds skyrockets like crazy. Why is that so?
When Tommy gets infected it is only a matter of minutes, maybe very, very few hours before he changes. Therefore the "infection" spreads quickly and affects the victim very powerful. I have no idea about how fast rabies deploys its malicious abilities, but I think the Zed-thing in WA is much more potent then that. Considering the situation of Tommy's and applying it 1:1 to many to most citizens of LA (and any other affected city, town, region, place, location) it might be valid to conclude that with a fairly small amount of infected only harming their victims instead of eating and killing them creates a powerful fighting force in a very short period time. Even if police-forces and military-forces react quickly, thoroughly and with all their skills and equipment, they are very likely overrun in minutes - especially in urban areas where all of a sudden hundreds of Zeds swarm in from different directions.
And yet: There are people that don't get infected - although they literally bath in blood and gore of the beasts. Just remember all of the major combat situations in the WA series where Zeds get torn apart, shot in the head or wounded etc., while they are right next to any survivor which - from a logical point of view - get bathed in or at least sprinkled with blood and gore of the infected beasts - and therefore get at least in touch with infected organic material. I know - very early on the show people assume that blood needs to be exchanged; therefore getting covered with the gore and blood might not be dangerous at all. But:
Tanya gets wounded (scratches on her back) while carried away at the end of season 2, and yet she has not become a Zed; Michael with his broken arm has some tight situations as well, which applies for Pegs with her wounded foot in "airwaves"; and what with Saul who was shot by Burt when Burt shot at the Zed-Tommy? I hardly believe that all of the survivors never have any abrasion or small wounds considering their overall situation. Therefore I assume that getting in touch with infected blood with at least small bruises or wounds is not so much of an issue, or there is something special to them that makes them kind of "immune" or "stronger against infections". (arguable though) But what I guess here makes more sense, if you just go on reading ...
Although the audience has no idea how many victims were captured and brought into the arena, and although there is not one source available telling the audience anything about how many people have died in combat or simply by being devoured, it may be a safe assumption that the number of those victims may be quite high - actually. In favor of this idea speak a few combat-facts: If most of the inhabitants of LA were Zeds, they wouldn't have any trouble overwhelming any survivor location, no matter how well the fortifications might be (just consider the huge power of the big ones which would have little trouble taking down fortifications or "weaker" walls); or if there were so many of the Zeds, the Mallers wouldn't have had any chance of getting near the arena with their trucks in order to burn the place. Since the numbers of Zeds cannot be so high, the Zeds rather perform strategies in order to capture people (like for example the artificial dead-end situation by blocking streets and attacking cars from all directions) instead of simply overwhelming them in huge numbers.
Again the question: What makes the survivors or the ones being captured or killed "special" or different from the ones having turned into Zeds so quickly? Or put in other words: What does a human body provide as a "quality" in order to be turned into a Zed?
Theory: It could be a very simple thing - blood-type. What, if all the survivors actually share the same blood-type, or at least a half-way match? Like A rhesus+, A rhesus-, AB rhesus+ and AB rhesus-, or the same with B and AB, or what about 0? This would explain two things:
a) It would be an explanation for people not becoming Zeds so easily - comparable with the situation along the black death epidemics in medieval times;
b) it would also explain, why some people turn to Zeds more slowly, like Tanya figured in her experiments, because the viral or toxic agent does not apply so easily to the victim's body.
Now, why are these ideas important? They may be important with regards to theories what may be more or less likely as a source of Zeds.
Radiation? Probably no; radiation is way to unstable with regards to the results and does affect any type of blood equally; also it would be kind of unreliable in terms of kicking off the Zed-campaign almost simultaneously in different cities and locations.
Nanobots? Probably same as with radiation.
Virus, bacteria? Maybe. And then: Who created it? And what is the purpose? Also: Why did some people change so drastically?
Simply a "mutagen"? Something that when getting into the blood-system starts to react with parts of the biochemical processes in the body of the victim; could be, actually. Same questions as with viruses, bacteria or whatever.
Chemicals, drugs, toxic stuff? Maybe; it is highly debated actually that certain "stuff" reacts with people different depending on their blood-type. Same with allergies or with medicine that works on patient no1 and not on patient no2.
2. Riddle #1
But there is a first riddle: the audience learns about a certain region in L.A. - somewhere around ground zero. If you get into it, people start feeling bad, nausea starts affecting them, and they need to get out of the region. Why is that so? Even months ofter the "outbreak"? And why didn't the survivors turn into Zeds themselves, because they drove through this area, if this strange nausea affect has something to do with Zeds?
If it were kind of a gas, it would not be fix on a certain location and/ or it would spread - due to weather, especially wind conditions. More valid might be a strong electromagnetic field or electric smog of some kind which is produced by a strong machine or device at ground zero, which is built to last (probably with a nuclear energy source, like nuclear batteries on satellites).
What would this do? Either it is there to keep none-Zeds away from the machine and therefore to prevent them from finding out more; and/or (!) it is kind of a physical device activating intoxicated victims who already carry the agent or the chemicals/ drugs/ toxics in them turning them from human biengs to Zeds. The latter case would also explain very well the at first low number of Zeds as well as the source when and where it all started. Also this would support especially the intoxication with some chemicals, drugs, or maybe mutagen, if these molecules are created in ways that certain kind of electro-magnetic frequencies might "activate" things ...
3. Riddle #2
And the second riddle is the one about the huge variety of Zeds. There are not only the standard-issue Zeds, but also big ones, small ones, jumpers, runners, clolored-ones.
Well. Good question:
a) If it is basically all about toxins, chemicals, agents of whatever kind, it may be valid to assume that different versions of these agents are out in the field.
b) Considering the fact that blood-types are about a lot more different attributes it may be safe to assume that the same toxic or drug reacts differently in the same general blood-type (let's say: "0"), if the other attributes of this blood-type vary a lot, therefore making the standard blood-type dude a standard Zed, while one guy with extraordinary a lot of dominant attributes in this blood might turn into something else like the big one or the colored Zeds ...
Anyway ... These things have crossed my mind. And considering the appearance of the "pinstriped suit" at the end of season 2 overwatching an ambush by the Zeds without being attacked, also considering the "attacks" in other cities at the same time as well as at least the shutting off of receiving broadcasts within LA it seems to be pretty obvious that something is going on which resembles the Resident Evil movies to some degree - like with the Umbrella Corporation doin' something; but it may be something deployed by military or public services as well, which I hold as less likely at the moment. To me all of this looks like a full-fledged attack against the territory of either the US or some/many/most/all nations world wide ...
What do you think?
All the best!