Talk:Green Flu

Two Things
One: Now that the game is out, and we know that the church guy was, or at least claims to have been, bitten, we can determine that the infected do in fact bite. This would mean that infection is passed through bodily fluids, much like the Rage virus of 28 Days Later. Two: Can we safely assume that the green stuff that Bill rubs on himself is Boomer bile? It looks pretty much just like it. --HarrisonH 07:43, 29 November 2008 (UTC)

That might explain why that horde of infected attacks them suddenly.I think the infected only bite those who are not immune or are dead.(Bill can be heard saying "If I go down,don't let those bastards eat me.")--76.208.38.216 18:57, 9 January 2009 (UTC)

True that he does say that,but most likely he is saying that because he is thinking stereo typical zombie(you haven't seen zombies eat anyone have you?-Gravhammer12 18:36 April 26 2009

''One: I disagree w/the assumption we can take Church Guy at his word. We cannot.   Conclusion: The church guy's behavior is insane and erratic and undependable, and his eyewitness testimony to his own experiences are circumspect in that they don't measure up to observation. Point of comparison: The sheer absence of young and domesticated animals reveals more in what's not said, than the church guy's words reveal in what is said. Where did all the kids, dogs, and cats go? There's not even corpses of them anywhere. Discovering that would tell us more about how this disease behaves and perhaps even how it is contracted. ''
 *  A) He may have been bitten during the attack, but the bite is not definitively what caused the infection. He may also be lying about being bitten, or misremembering. He's not in his right mind when we encounter him.
 *  B) IF this is a genetically modified strain of rabies, the fact rabies is transmitted via saliva does not necessarily mean that's how this Infection must be transmitted. 
 *  C) There are no observations that indicate the Infected eat at all. Seeking shelter, water, food, or a survival instinct of any kind are absent in their behavior. We never see them eat, much less bite the survivors, or one another. 

''Two: The Boomer Bile may explain how some observations would lend credence to this being air-born and other observations seeming to contradict that. What if this Infection were air-born but only for short periods? What if the only way to contract it would be via Boomer Bile? Or perhaps to a lesser extent, when a Smoker detonates? Again, our Survivors are immune for currently unknown reasons (maybe they'd recently had their rabies shots?), but if every time a Boomer or Smoker explodes, any non Infected who inhale the air born bile would contract the disease. Said Boomer Bile might quickly lose its effectiveness after a short time exposure to the open air and the elements. Some could have come in contact with the Infected and not acquire the disease, unless a Boomer was involved. This would also explain perhaps where the children & domestic animals went. If prior to puberty, a human host body can only mutate into a Boomer, but some adults (or perhaps all eventually) can mutate into the other Special Infecteds, that would cause the disease to spread much quicker (within two weeks easy) especially since most parents wouldn't want to leave their child's side even after s/he began to show symptoms. The only thing I see that ruins this theory is the lack of reaction to all the children disappearing: no mention of it in the graffiti and no discussion of it among our Survivors. Perhaps they don't know, but one would imagine if all the children and small animals of the city exploded, there'd be some mention of it. ''

''Of course, all this is mere speculation, but based more on observation than the presumption that biting is at all involved. We never see the Infected bite anyone.'' - ZachsMind 22:47, 19 March 2009 (UTC)


 * As aforementioned, Bill states not to "let these bastards eat me," and occaisionally, after being incapacitated and revived, Zoey will say, "I have tooth marks on me"

Waterga74 23:11, 20 March 2009 (UTC)
 * You certainly have some interesting theories there, mister. I, myself, think that the Infection is spread primarily through oral contact, saliva in specific, as it is a strain of hydrophobia.  Also, as Waterga74 said, they talk about being eaten and bitten.  The lack of oral contact is probably more to do with game mechanics than the actual nature of the Infection, as is the distinct lack of children—which I will touch on in a moment.


 * How do you think you'd work in the biting into the gameplay of Left 4 Dead? Would a zombie or two or three or more hold you down and try to bite you, and you'd have to press buttons really fast to get away (like in Resident Evil)?  Would they just sort of casually nip at you while you're moving?  What's the point of animating something you're probably not even going to notice, anyway?  It's probably much easier to have them slash and smack and whatnot.  Also, the zombies probably have to eat, maybe they eat their victims, but showing them eating when they're supposed to mercilessly barrel at you.  Left 4 Dead isn't much for storytelling in front of your eyes, it's more of a story you have to read in between the lines to figure out, like looking at the graffiti.  I think that's what helps to make Valve's games so...fascinating.  I mean, look at the Half-Life series, and think about it.


 * Speaking of graffiti, have you seen the message a certain Will wrote? "TO HELEN LANE, DAD AND ME LOVE YOU AND WE ARE ALRITE - Will"  It looks a lot like it was written by a child, doesn't it?  I think the children are out there, but you don't see them in the game because that's basically a taboo in video games, it seems.  You can't kill children.


 * I do like your ideas about how the Boomers and Smokers tie into it, though. Very well thought out.  You most definitely bring some intriguing aspects onto the table. - §tigma-231  ¤ ৳ here's a  hole  in my neighbourhood [ talk  ][ cont ] 00:38, 21 March 2009 (UTC)

Cows
It has been suggested here that cows may be the cause of the infection. Two reasons: What are your thoughts? --HarrisonH 00:34, 2 December 2008 (UTC)
 * 1) In Blood Harvest, there are piles of dead cows. Their bodies seem to look odd, compared to our cows. Also, why would they be in piles?
 * 2) In the tunnel thing at the beginning of the finale of Dead Air, the signs say that you must contact security if you have been in contact with any livestock in the past 48 hours.

I think that the virus originated in cows, then thousands across the globe consumed the meat, only to mutate into the infected. Perhaps the pile of cows bodies was the armies attempt to kill off the virus in bovines, not realising it could spread through bite aswell? The DJ 14:54, 28 February 2009 (UTC)

Actually, since the infection is assumed to be a form of rabies, it would come to reason that animals are tested for rabies. This is generally done by testing brain tissue (which would, of course, kill the animal). With the extend of the infection the military probably killed all lifestock as a precaution and performed the tests to map where the virus had spread. We can not say for certain that the infection started with livestock, just that they were killed and tested as a precaution. -Tiger Well one thing crosses out the idea that livestock began the infection because in The Hospital chapter of No Mercy, there is a room that has quarantine all over it,and if you go in there it has an X-Ray of the signature hand icon for L4D. Also, the piles of cows suggests that maybe aliens caused it.
 * ...Wait, what? Sorry, but that really makes no sense.  If it was caused by livestock, that means the products produced by livestock (such as meat or things like milk) may have carried the virus.  The dead cows suggest that they slaughtered the rest of the livestock in hopes of quarantining the possible source of the Infection, to prevent others from being infected.  The Infection is a mutated strain of the rabies virus—a disease which exists on Earth.  Do you not understand evolution, my friend? - §tigma-231  ♠ ৳ hаt i ɯill nəvər escaρe [ łalk  ][ ςont ] 01:55, 27 April 2009 (UTC)

I think it is most likely to be a mutated form of mad cow disease, "mad human disease." The Deep 1 22:18, September 20, 2009 (UTC)

Quick FYI
According to the game's strategy guide,people been reported being sprayed with infected blood during combat and did not turn into zombies or show any signs of infection.It also says no one knows why the infection appeared,but it says that the zombies are not rising from graves.It also says that there is a large amount of false rumors about the infected and that CEDA is partially responsible for their circulation,but it's mostly the public spreading them.--76.208.58.137 23:58, 2 December 2008 (UTC)

''It's plausible that the writers of the game do not themselves know for certain what the actual answer is, but left enough clues to suggest multiple possibilities, so fans could debate over it indefinitely. Hopefully though they made it a puzzle of sorts that can be sorted out with the evidence, and that there is an actual answer. Otherwise, debating over it would be futile, thus taking the fun out of such debate. However, as there is no evidence of aliens throughout the game, we can probably rule that one out. The fact the military actively efforts to save our Survivors at the end indicates they did not wish to leave them for dead. However, that alone doesn't fully remove "Government Conspiracy" from the table. It does indicate its unlikely. The gov't could have just as easily not rescued our foursome and just nuked PA from orbit.'' - ZachsMind 22:59, 19 March 2009 (UTC)

You shouldn't really take those strategy guides into context unless they're written by valve, and, unless you have a different one than I have seen, its not. Strategy guides can and usually are, total and complete bullcrap. Sure, its possible thats right, but almost certainly not. It, like other similar viruses, is airborne. How else could it spread to the entire state of Pennsylvania in two weeks, and all the way down to Louisiana in three?--Supermutantslayer450 22:35, September 16, 2009 (UTC)


 * Quoting some random dude that made some graffiti: "NOT AIRBORNE". However, you do got a point there, no other means of infection would make it spread so quickly, but let's take into consideration the Church guy wasn't immune, yet he didn't got infected until he was biten... DeathBlade182 02:09, September 17, 2009 (UTC)

The Infection
My theory for the infection is that it is directly related to cows and fast food. I think the cows were given something to increase production or something which in turn were sent to restuarants. Eaten directly by future boomers and common(did not eat as much). The virus creating special infected mutates from what the host has in their body(tank-perhaps steriods)(hunter-drugs)(boomer-ate hamburgers a lot, direct contact with the source of the infection)(smookers-chemicals in cigerates and cigars.) This is my second comment so I don't know if I did something wrong our what. sidenote-cows farmhouse finale thing or some other level(dont have game) are dead in piles and in dead air a poster says to contact security if u have been in contact with livestock in the past 48 hours. i dont firmly believe this but it sounds kind of logical. no theory on witch yet (please leave comments on this page) XboxBoxLiveGuy321 23:51, 12 December 2008 (UTC)

I laughed at the hunter's explanation. drugs? what? =P the boomer coming first makes sense, since it was the first special infected developed.

actually, I understood that the special infected were just mutations. for example, a boomer may have resulted as the virus affected the gastrointestinal system drastically.

All the infected have a special role against the survivors, aside from teh witch.. The virus may have just mutated into these to make sure that the remaining survivors were infected or at least killed, to protect its own life. Waterga74 22:59, 28 February 2009 (UTC)

My theory on the boomer is when a REALLY fat person gets infected, a hunter when a person on dope, pot, or crack is infected, a tank is when a REALLY strong dude is infected, and smoker when a smoker is infected. no theory on witch-76.172.80.140 23:21, 13 April 2009 (UTC)

It actually sounds quite possible that a pharmaceutical company could be to blame by that reasoning. I mean think of how many items you use everyday that have some sort of chemical in it. You literally have to TRY to avoid them. Eveything has something in it. Perhaps a pharmaceutical company could have discovered a "wonder drug" used to increase the growth rate of things, kind of like a Fountain of Youth (Resident Evil-ish) and started mass producing it without proper testing. Farmers would use it on beef in the form of some ROIDS shots or fertilizer for tobacco.

It would almost kind of explain the cows, and why they were killed. Though it does kind of open up a problem for the loads of pills all over the place, but then again we don't know the time frame of the entire attack, who says the Survivors aren't infected... Stoan04 14:05, 27 March 2009 (UTC)
 * The Boomers ate at McDonald's too much, and the substance had large amount of contact with the intestinal tract. This would explain the bloated, blob look and bile abilities as the substance altered the internal organs substantially.
 * The Smokers obviously are smokers, the substance would have a large amount of contact with the lungs and mouth. This would explain the altered tongue and coughing.
 * The Tanks could have got ahold of some of the ROID shots and used it directly, explaining the huge muscles as the substance did wonders on muscle growth.
 * The Hunters got some altered form of it cause it gave you a good high. Doesn't really explain the jumping and screaming, but they do look like thugs.
 * The Witches used another altered version for a weight loss pill, as the substance could be used for growth of organs that increased metabolism. Which as stereotypical as I can be, would help explain why all the Witches are young-ish, thin females.
 * The Common Infected just happened to get it from small everyday usage, not really altering particular parts, and they didn't get it in heavy dosages.

What about the pain pills though? IF the medicine companies were to blame, why did the pain pills survive without a disease in it?

Maybe This Is How The Infection Started?
Obviously most people who play Left 4 Dead are wondering this. How the hell did the infection start?! Well, I think I might have an answer! The man who you see in Mercy Hospital behind the yellow Bio-Hazard tapes (Most likely donated by our very good friends, CEDA.) is most likely the origin of the infection. The infection must have started somehow, maybe it just came? Maybe it Evolved from another disease, such as Rabies. Well, this man went to hospital feeling ill. After they did some testing they found out he was carrying some sort of disease, but they couldn't tell which (As it was mutated!) so took him to a special care ward (That's why it's only one room, one bed at the end of a corridor near the top of the hospital: Where most real life special care wards are kept). Eventually he started to turn into a Zombie. Maybe when he was being tested on/operated on he bit a Nurse or Doctor, causing them to become infected. Eventually as more and more of them [Hospital Staff] became infected they started biting the patients, who in turn became infected. Eventually this spread out of the hospital and into the city/town. Then it just kept spreading, maybe some people got on a plane and set off for a holiday in the Bahamas, then that became infected and so on and on on. We know that within two weeks the military has tried [and failed rather epically] at containing the disease and just about everyone becomes infected. The survivors we know, are Immune to the infecte, as they might have a certain blood type, maybe better immune systems, maybe they can just reject the infection. We know the infection must have started in the North as when we start playing as Nick, Coach, Rochelle and Ellis in Left 4 Dead 2 we start in the south, which is new to the infection. The South, who know at dealing with the infection a bit better than the North, start bombing the hell out of New Orleans and many other cities/towns. This kills the infected, but alas also kills any people who are still alive/not infected. Going back to the North now. When you get to Dead Air you see the huge plane crash in an amazing fireball which would put a large Bonfire Night out of it's misery you wonder. Wait? If it crashed just now then mustn't that mean that the Pilot and Co-Pilot were still alive for a while, as I'm sure Infected can not fly an Airbus. Maybe there was one infected person on the plane, who infected all the passengers. The Pilots knew this and sealed themselves inside the cabin, hoping to land and leg it to safety (Inconsiderate bastards), but the pue number of infected on the door must have broke it, and the captain and co-pilot were either bitten or killed, so the plane crashed due to no one flying it. I also think that maybe the pilot knew everyone wa infected, but maybe though that the people in town were still alive, so he crashed the plane on purpose. If he did this then that man sacrificed himself to save a town [which was already overrun]. I think he deserves a medal. --WaffleMania 16:33, October 18, 2009 (UTC)

Information
Where are you guys getting the facts that the Infection is a virus, not a bactirium or Protist. Also, where is the rabies part coming from???
 * I'm pretty sure Valve themselves have confirmed it at some point. But, now that you've brought that up, I think we should probably start adding some references to things like that, just to make sure everything stays clear and legitimate. - §tigma-231  ♠ ৳ hаt i ɯill nəvər escaρe [ łalk  ][ ςont ] 02:08, 26 March 2009 (UTC)

Another question, where is the "Possible first infection" section in the article coming from?? this is speculation/opinion

Guys, sign your posts. TheCreaturenator16 19:15, 27 March 2009 (UTC)

Mercy Hospital?
I noticed this on a recent playthrough; the IV bags found near beds at Mercy Hospital all have "CONTAMINATED" stamped in big red letters across their front. While I am unsure of hospital procedure (maybe they stamp it as such as soon as they tap it, since it can't be used on a different patient), it seems suspicious that everybody in that ICU was getting fluid marked as contaminated. Raptor22 04:08, 31 December 2008 (UTC)

''This behavior can easily be explained as a variant on the "Typhoid Mary" scenario. The hospital is overrun and there are many doctors and nurses doing everything they can in a crisis. One or more medical personnel notice a nearby blood bank is later reported to be overrun by Infected. Naturally they would assume that blood from said bank is also Infected, or at the very least compromised, and so they would mark that to separate it from the blood they still perceive to be good. Meanwhile, another one or more medical personnel, realizing they are rapidly running out of blood, would notice the "contaminated blood" and demand to know why its been marked thus, probably because there is a protocol to follow which due to time constraints the first group of medical personnel would have overlooked. The second group of medical personnel, ignorant or wary of the evidence the first group has regarding why such blood is presumably contaminated, would start using it anyway. This second group of medical personnel would be our "Typhoid Mary" group. They would perhaps be spreading the contagion, but refuse to believe any evidence contrary to their opinion. Point of fact, two weeks after contamination, there's still no evidence to suggest that blood is how the disease is transmitted. The second group may have been correct in saying the blood was fine, but they all died in a futile effort to save their patients anyway. Do remember there's a point in the hospital where we see an area cordoned off with yellow police tape. It's possible in that part of Mercy Hospital we might find the remains of "Patient Zero." '' - ZachsMind 23:32, 19 March 2009 (UTC)

iv bags
i think that during the infection and realising that some people were infected meant that some of the blood people have donated had been infected and there were trying to keep the infected blood out of the system.I assume as soon as doctor realised that a blood pack had been infected blood in it they stamped the contaimated stamp on it to stop the same person blood being used on someone elses but due to the chaos and panic of try to figure out which blood packs they could still use they ended up.Or someone was testing the CONTAMINATED blood in the hospital and that it went wrong and overwelmed the hospital

--Spygon 09:44, 31 December 2008 (UTC)


 * Could have spread through livestock then infected humans which then spread through biting, blood, and saliva. 69.12.204.67 10:00, 31 December 2008 (UTC)

the date
maybe this is not relevant for the infection but i read on the walls of many "safe rooms" R.I.P.s with the date on october-13-2009. maybe the infection started this day, on october 13.

also i read that the infection takes 5 min to 4 days to change you.

Okay, I realize that this was made a while ago, and this person didnt sign... but the blog on the l4d website says that the developing staff died in november. Maybe this has something to do with those deaths.. Waterga74 01:57, 18 March 2009 (UTC)

Seeing as the times taken to transform lower as time goes on (as each survivor writes an answer on the wall lower down), it is a possibility that The Infection continues to mutate, and is becoming more powerful/potent over time. -Bale, 06 June 2009

Immunity Trivia
I think there's a slight misunderstanding so far as speculation goes regarding the immunity of the survivors. All viruses, even those which are extremely common, are going to have people who are immune to them. Doctors are still actively researching why this is the case as they feel people who are immune may give us some idea as to how to get rid of such illnesses. But as it is, there are rare cases of people who are immune to Ebola hemorrhagic fever, AIDS, influenza, and so on. Something like this, that hits pandemic levels extremely quickly and changes people so drastically, would just stand to exemplify those with immunities.

That being said, the fact that the survivors are immune to it does not imply that it is a germ warfare agent, nor that a cure can be made any moreso than we can cure AIDS or the flu. (digiwombat | Not currently signed up) 76.170.233.156 22:06, 17 February 2009 (UTC)

That guy's smart. =O

But he's right. Viruses are just incredibly small organisms, smaller than germs. They alter the DNA of cells to produce more of the virus, which spread farther. This applies to all viruses. Some immune systems can, however, defend against them efficiently.

Waterga74 22:54, 28 February 2009 (UTC)

Viruses are germs too--User:TeriffiedToxic Life as we know it will end soon I think.. 08:43, 14 July 2009 (UTC)
 * As long as Valve still needs money, the Left 4 Dead world will exist with sequels forever and ever. ;D Zikkun 08:48, 14 July 2009 (UTC)

''I'm working on a theory that one possible reason why Bill, Zoe, Louis & Francis are immune is because perhaps they have each relatively recently had standard rabies shots. We are led to believe that many people successfully took the route this foursome has. In fact, perhaps one or more of them helped orchestrate this string of safehouses and are now the last ones to run the gauntlet to safety. It's plausible that immunity can come from some small recent change to how rabies shots are done, and any adults in recent years who have had rabies shots would be immune. There may also be a number of immune people who didn't make it because they weren't capable of escaping due to lack of gun knowledge for example. This would not apply to childrens' rabies shots, which might help to explain why all the children obviously died off first. This theory however is dependent on yet another theory that the Infection is somehow artificially or naturally related to previous strains of the rabies (aka 'hydrophobia') virus. If it's not, then regarding immunity, I'm back at square one.'' - ZachsMind 23:58, 19 March 2009 (UTC)

Waterga74, viruses are technicly "Germs" because the definition of a germ is a microorganism that causes diseise. --Djj51 02:52, 20 April 2009 (UTC)


 * Not all viruses cause disease, as many viruses reproduce without causing any obvious harm to the infected organism. Some viruses such as hepatitis B can cause life-long or chronic infections, and the viruses continue to replicate in the body despite the hosts' defence mechanisms.  Taken straight from http://en.wikipedia.org/wiki/Virus . Stoan04 14:14, 27 March 2009 (UTC)

Stoan, what you are saying is correct, but that is not what I ment. Waterga stated that viruses were smaller that germs and some viruses are germs (disiese causing organisms) --Djj51 03:14, 30 March 2009 (UTC)

Technically, are viruses even considered living things? Since all they have are a protein coat, the RNA and whatnot, and the flagella on some to help move around. Other than that, there are no organelles or nuclei. (This is Blacklite, by the way.) 66.203.20.163 12:23, 30 March 2009 (UTC)

I would assume Viruses are considered living as much as our own cells are, or even sperm, which I would assume are basically the same size (and do basically the same thing...). Stoan04 15:25, 30 March 2009 (UTC)
 * From Wikipedia:

"Opinions differ on whether viruses are a form of life, or organic structures that interact with living organisms. They have been described as "organisms at the edge of life", since they resemble organisms in that they possess genes and evolve by natural selection, and reproduce by creating multiple copies of themselves through self-assembly. However, although they have genes, they do not have a cellular structure, which is often seen as the basic unit of life."

I honestly think that viruses aren't living things, and just micro-organic vectors that solely spread disease and nothing else.BlackliteWrath 12:36, 14 April 2009 (UTC)

Some microbiologists classify viruses as nonliving, because all they are is a string of DNA and a protein coat, and that they don't fit into any of the seven kingdoms. But, then others say they are living due to their infectious manner.--Djj51 02:52, 20 April 2009 (UTC)

Pathogens: Comparing fact to fiction
''One point that I have not noticed anyone else make is that this is no ordinary pathogen. Viruses like AIDS and rabies and ebola damage tissue and even affect on a rudimentary level some behavior patterns among the infected. Particularly rabies with the latter, and ebola with the former. AIDS only seems to attack the immune system of its host, making the host more susceptible to other pathogens. In other words, AIDS appears to specifically target its host not to kill it, but to allow the host to be killed. This is counter intuitive to a survival instinct of more advanced living things. Viruses that we know about tend to purposefully endanger the future of the host, therefore limiting its own future as well. There's no survival instinct. However, the host him or herself is still cognizant the entire time up until death and actively in most cases persuing avenues of departure from its own demise.''

''This Infection removes from its host the will to live, and the will to allow anything else live. It appears systematically designed to decimate the human race. This Infection isn't just targetting the immune system or the digestive system or causing discomfort that leads to erratic behavior. This Infection affects the very nervous system of the hosts, turning them into agents for its own demise and that of its target. The thought of it is actually rather fascinating. ...well if it weren't so creepy it'd be fascinating.'' - ZachsMind 23:47, 19 March 2009 (UTC)


 * Well, heck, he's got us screwed. Waterga74 23:08, 20 March 2009 (UTC)

Special Infected
I believe that the infeced have changed more along the way, or the virus is still taking its course. At the begining of the game, Bill says that the infected are "changing", when Zoey and Bill see the Witch, they had no clue what she was...because they had never encountered her before. Now after two weeks, they surely must have seen a Witch at least once. This leaves two possible conclusions:

--A: All 4 of the survivors have been living under a rock.

--B: The infected are changing and/or adapting.

Once the game startes, they have established nick names for the infected from what they have seen, and how they act. A scarey thing about this is, after two weeks this is what the infected have adapted to, after two MORE weeks, there will be more infected that have converted, and possibly new types of infected. Imagine, all of the normal and common infected are now all special infected, no "plain" zombies...The world of L4D would end quickly. It appears that for the infected to become "special infected" it takes time, such as first meeting them after two weeks (which would mean, it took the original zombies 2 weeks to change to this), which would mean, the special infected that they are fighting now, were the first to fall to the virus. However, time to become an infected could vary between others, such as how some fall to the virus in seconds, some in days while others are immune. Example, the "Church Guy" became infected an hour after he was first bit, therefore, it took him a short while to become a special infected. While others, who become zombies days after they were first bit, may become special infected days after they become a zombie. --User:Monobrow1

your logic to them "adapting" is logical, however, I had assumed that they were just mutations among the ordinary infection, causing strange appearances and "growths." As you said, the church guy transformed in like, and hour to a special infected. So yea. I'm sticking with "mutations." Waterga74 14:22, 23 March 2009 (UTC)

Mutations of the infection is probably the best way to explain the Specials. I mean as Waterga pointed out, Churchguy turned into a Special within an hour. But both of you could be correct, the Infection as pointed out numerous times is not normal. As with other things, viruses and bacteria are going to do different things to different people. It could take a while for the Infection to overcome your Immune System completely leaving you as a Common until it did, and afterwards it turns you into a Special. Or you could have a weak immune system, due to Pneumonia or HIV/AIDs, allowing the Infection to get started and get done quickly. So depending on how your immune system is, it could take weeks, days, hours, minutes to turn you. Even the graffiti on the walls shows it could take different amount of times. Or mayhaps, the virus is adapting and becoming stronger. Stoan04 14:24, 27 March 2009 (UTC)

I think the special infected came to be because they have survived longer than regular zombies. Regular zombies only survive a couple days, while special infected have changed over alot of days. So if a regular zombie stayed alive long enough, they may turn into a special infected. Camster103 22:10, October 21, 2009 (UTC)

Insects
I believe bugs are immune,as you see a fly in the intro movie,unnafected by what it`s eating.Bigens 23:39, 4 April 2009 (UTC)

Well that says nothing about what is immune, I opt to change the name to insects, anyones opinion. --Djj51 03:00, 20 April 2009 (UTC)

There.Bigens 03:12, 20 April 2009 (UTC)

I think that if there WERE infected Insects in the game, wouldn't there be some sign of them being infected? Such as the insects swarming around the Survivors, even being harmless at best. But then again, that would be too annoying for the players and the programmers. But then again again, there should be some signs outside of affected the Survivors that insects are infected. BlackliteWrath 11:53, 20 April 2009 (UTC)

Yes, but insects are so far away geneticly from us that they would be unaffected, the only other animals that might get infected are pigs, monkeys, and apes --Djj51 21:50, 26 April 2009 (UTC)

Extent
do to the 4 areas that the game takes place in, it is possible that the Infection could only afflict the Eastern coast of america. --Djj51 21:15, 17 April 2009 (UTC)
 * Indeed, but judging by how hard it seems to be to find a safe place from the Infection, and how illnesses like to spread around like wildfire, chances are it's spread to other regions of North America, maybe even beyond that. Maybe somebody who got infected, but didn't know it at the time, boarded a plane to the other side of the world.  It only takes one person to spark a flame. - §tigma-231  ♠ ৳ hаt i ɯill nəvər escaρe [ łalk  ][ ςont ] 05:19, 18 April 2009 (UTC)

i agree with stigma as i feel the situation is either like the 28 days later way where the whole of the usa is infected but the other countries have quarantined the united states or the more likely situation where the infection is worldwide as it seems to have spread so quickly in 2 weeks and theres no sign of any other nations trying to help out the areas.Spygon 12:46, 18 April 2009 (UTC)

Yes, but in only two weeks, the tree cities and the forest where overrun, on the assumpsion that the infection started in one of the cities, it is possible that the airports where quickly quarantined, and the military set up rescue areas. why would they do so if there was no place to go to in the end, think of the movie I Am Legend, in the begining, he acts like he is the last one left, but later on new people are introduced, and an entire colony of people is still alive. this transfers to left 4 dead in the way that a highly infecuous diesise has trouble spreading due to a tiny fraction of the overall population of an area. If 50-75% of all survivors escaped the areas of left 4 dead, then they could just go the couple THOUSAND miles across the U.S. and find that life is unchanged there --Djj51 18:33, 18 April 2009 (UTC)

but thats the thing with i am legend the people that are found are other survivors and the camp is a camp full of survivors the army show no sign of being around as i feel this would be the same in the world of left 4 dead as there would be small groups of survivors hanging on by there finger nails.As we know that during the first 2 weeks of the infection the army have been on the back foot and everytime they have tried to control the outbreak they end up being overrun so as the way it has deverstated and infected at least 95% of the areas population i would feel that is has spread like wildfire across the country at least.Also with how many infected and corpses around i doubt that 50% managed to escape to be honest at the very most your looking at 10% of survivors getting out of the area.So with how many people are in close proximity to each other the infection would spread through most areas of the usa stupidly quickly.Spygon 09:23, 20 April 2009 (UTC)


 * On this subject, we can be sure that there are small groups of Survivors are still alive. In No Mercy, machine gun fire can be heard in the distance. The spread of the Infection, however, leads me to believe that most of the large cities on the East Coast have been overrun, and depending on the response time of the military, aircraft could have taken off and infected cities around the country; maybe even the globe! Where did the plane in Dead Air come from? There has to be military installations somewhere, where they have been able to hold out. Piranha Talk to Me [[Image:Demon_Razgriz_Logo.jpg|30px]] 21:23, 8 May 2009 (UTC)
 * If you check the map in the Finale of Blood Harvest in the farmhouse by the radio, at the top there is a section marked "Safe Zone". This is the "Military safe zone up north" that the helicopter pilot referred in the cut sound files. You'll notice it is a rather large safe zone, looking down and comparing them with Riverside, Fairfield or Newburg. That is most likely where this "military installation where they have been able to hold out" that you asked about is located. -- Five Dog ( Talk ){ Updates } 16:34, 31 May 2009 (UTC)

Well,part of this theory just got torn to shreds, due to parts of L4D2 being in New Orleans --Djj51 13:46, 6 June 2009 (UTC)

Yes, but this happens about a week after left 4 dead (correct me if im wrong) and the first campaign of L4D2 is set in savanah where the infection is just gettin to, meaning the infection has been less destructive the originally thought. as the south is only just getting infected 3 weeks after the first infection, that means that the infection was quarintined much more effectivly than thought in the north, so the rest of the world might be just getting hit, if its even spread outside the US. --Just Some Guy720 15:34, October 10, 2009 (UTC)

Animals and Children
I am going to attempt to explain why there are no infected animals or children in the game in both practical and game-canon perspectives. The children and the elderly are probably just killed by the infection rather than mutated. Also, shooting children and old people would probably just detract from the game, not to mention get complaints. Animals may be immune, because you can hear dogs barking in the distance, not to mention the rats that can be heard and the crows in Blood Harvest. The dead cows were probably killed by humans, because why else would they be stacked in piles? From a practical perspective, animals would be hard to incorporate into the game. Also, they would be annoying. That is one thing that was annoying in Resident Evil: zombie dogs. They did nothing but annoy me. TheCreaturenator16 05:10, 13 July 2009 (UTC)

I have to agree, Valve did so to avoid getting complains seems explainable. Take a look at Resident Evil 5, most players just call Capcom racists now. Animals' might be hard to answer on the developers' side, but I guess that the virus that turns people into Infected just doesn't effect animals if you put it canon-wise. The cows are really odd in my opinion, other animals are not seen, there is a sign in Blood Harvest that said "Deers in the way", this could mean that most of the animals just tried to run-away because we don't see them. I think it's just Valve's doing, they also removed all the Children in Half-Life 2 not to make references such as the Ghetto, and so they did so in all their games. Zikkun 06:11, 13 July 2009 (UTC)
 * Also because it's apparently wrong to kill children in video games. I can't think of any game where it's allowed...  But that's also partially because PETA would make Valve become an hero with their incessant whining after, I'm sure.


 * Now that you mention that, I barely recall deaths of children in video games. Well... I remember killing 2 years ago a kid in RollerCoaster Tycoon 2 by mistake because my ride was epicly bugged, can I sue Atari?>.> The children are understandable, but why animals? Valve's Headcrabs somehow count as animals in my book. Zikkun 08:37, 14 July 2009 (UTC)


 * Like that fly. - §tigma-231 ♠ o  ƒ  my caliber { τalk }{¢ont } 20:40, 13 July 2009 (UTC)
 * Oh, that's another thing. Totally off topic, but come on, who hasn't smacked a fly? I support a lot of PETA's views, but some are just out of hand. But I digress. TheCreaturenator16 06:41, 14 July 2009 (UTC)

In Fable 2, Rose got killed at the beginning of the game, and that was up close. On Fallout 3, if u decide to blow up Megaton, you will kill 2 kids. Fallout 1 and 2, you can kill kids, but the company doesnt really want you to, and killing 1 child has more severe consequences than murdering an entire town.--Supermutantslayer450 22:28, September 20, 2009 (UTC)

Let's not forget Little Sisters O.O Oh and in Resident Evil...4 I beileve you can kill the girl you are protecting or just let her get killed...And staying in the Fallout 3 topic... They won't let you kill kids, no matter how much you hit or shoot them, they are invincible.

Elite-Nachos 04:55, October 25, 2009 (UTC)

Yeah, but if you blow up Megaton, two kids are in there,they dont get out, and theres no way anyone can survive a neclear explosion if they are right next to it.--The Scat Man 450  RO A  R! 16:26, October 25, 2009 (UTC)

Rabies
i have readed many threads that say that it has been confirmed that the infection is mutated rabie...but why cant i find the original post, can YOU link it? Gesmana 05:58, 30 July 2009 (UTC)

The Hunter - The only infected to bite in-game?
I was going through the hunter's model animations the other day, and found somthing of note: The hunter bites people it pounces. or at least it appears to, leaning down to roughly the target's neck area, with a Gore splattering sound playing upon "contact". Can anyone else check this using the left 4 dead authoring tools beta? There's normally too much else going on to spot it in-game. I'm not sure myself, but I beleive it warrants discussion. --AstralShapeShifter 22:21, 3 August 2009 (UTC)
 * Indeed it does bite. I checked it out myself in the SDK. Darkman 4 00:56, September 9, 2009 (UTC)

Possible origin for the witch
as we have defined in the talk above, the virus affects different people in defferent ways. seeing as there are common women infected, we have to assume that there is somthing different about the witch. Is it possible that the witch might have been a woman who had a personailty disorder before the virus?

Not a personality disorder, the Infection apparently destroys most higher brain functions, so this wouldn't affect the person. perhaps the witch was once a person who took slimming drugs because they thought they where fat. The drugs could interact with the virus to create the witch. The witch crying is probably a tactic to draw in the survivors.--Djj51 17:14, October 1, 2009 (UTC)

Thats quite possible, but its also possible that the witch could be what happens when the tank strain infects a woman. think about it: witch and tank are both strong as all hell (the witch is actually stronger then a tank) both have higher health then all other then infected and both are moody as crap ( witch goes from sad to angry to coward in 3 seconds if playing on expert and i aint never seen a happy tank. you guys?) also she could have much more devloped legs then the tank seeing as shes faster then him, and the survivors, instead of the bullet immunity and concrete detector the tank has. or this could all be incoherent babble cuase im pretty tired :) --Just Some Guy720 15:28, October 10, 2009 (UTC)

Carriers
Hi, would probably be good for someone to add in a section about those with Immunity to the infection still being able to carry the infection. This can be assumed from the graffiti in Left 4 Dead 2 in the various safehouses...