'Infected' refers to humans who have been infected by the Rage Virus that originated in the Cambridge Primate Research Centre. Highly contagious and spread through bodily fluids such as blood and saliva, the virus takes over an exposed host within 10 to 20 seconds. Symptoms include constant spasming, and internal bleeding from all bodily orifices as well as hemoemesis. The Infected exhibits no goal or trace of their former-selves. The individual simply expresses constant rabid all-consuming rage with a single-minded drive to always violently attack and pursue any uninfected individuals they find. Though Rage does not kill its host directly, lacking the instincts to find food, the Infected do eventually die from starvation. Infected lack a sense of self-preservation, and will not act to evade or respond to mortal danger.
The virus' easy transmission, very short incubation stage, and consequently rapid spread among the populace easily makes it the most destructive pathogen in human history. Like a falling dominos, a single infected person is all that it takes to wipeout many large populations, and cause global societal collapses. However, the virus' inability to infect non-primate hosts, and relatively rapid starvation-deaths of the infected means it is possible to isolate and quarantine an area from surrounding regions.
A human, chimp or other primate that is exposed to the Rage Virus through bodily-fluid contact - such as a bite, a kiss, an injection or infected blood in their eyes or mouth - will become Infected in between ten and twenty seconds, with the Infection within that time violently infecting and overwhelming the exposed person. Once a victim is exposed to Infection, it would appear that the amount of time it takes for the Rage Virus to fully infect and take them over depends on how much Rage they were exposed to; Frank, after a drop of infected blood fell in his eye, took a few moments before the Virus began to take over, while Clifton became Infected almost instantly after an Infected vomited blood directly into his face. (28 Days Later (film))
The Rage Virus causes the Infected to experience spasms in their extremities, (28 Days Later (film)) and their irises enlarge and become blood red. They also regularly, if not constantly, bleed from their bodily orifices (such as their eyes, nose, mouth and hair follicles), and vomit copious amounts of infectious blood; due to internal hemorrhaging that the Virus causes.
While the Infected do eventually die from starvation (due to their immense and single-minded rage towards the uninfected causing a disregard for self-nourishment), they seem to be able to last longer than uninfected individuals without nutrition, to the point that the Infected can last for up to eight weeks or less before becoming too weak to move. (28 Days Later (film), 28 Weeks Later)
Intelligence and behaviour
The Infected are shown to retain some intelligence from before they were infected, including spatial awareness, as they can calculate complex routes to unseen targets. They are also aware that if an uninfected victim is already dead, then they cannot infect or kill it themselves; this was shown during the Second Outbreak, when an Infected grabbed an uninfected woman, but when the woman was shot and killed by a sniper almost immediately, the Infected immediately tossed her aside. (28 Weeks Later) The Infected showed some intelligence when a horde of Infected attacked Frank's taxi in an underground tunnel; when the uninfected group escaped in the taxi out of the tunnel, the Infected gave up the chase, seeming to know they had as good as lost them at this point. (28 Days Later (film)) Infected have been observed to, when inactive, simply lie amongst corpses before being alerted to the presence of uninfected; perhaps due to lack of any uninfected individuals around, or because of their nocturnal nature. (28 Days Later (film), 28 Days Later (comic series))
The Infected apparently retain basic problem-solving intelligence, as the infected Don Harris used objects such as an M4 rifle as blunt-force weapons, and the Infected have been known to go through doors, windows and entrance points and navigate around other obstacles to reach sources of possible uninfected activity. It has also been shown that the Infected prefer to attack victims that are easier to kill or infect. This was shown during the attack on Geoff and Sally's farm, when an Infected tried to attack Don Harris; when Don locked himself in a room from the Infected and the Infected was unable to quickly break in, the Infected almost immediately turned their attention to attacking Alice and the boy from Sandford instead. (28 Weeks Later)
At least one Infected, Donald Harris, was shown to possess intelligence that was usually devoid in the Infected; he displayed fragment memories of his family, to the point that after he was infected, he began stalking and following his children. It is also believed that the infected Don remembered how to operate basic machinery, as he was able to escape Alice's isolation cell, something he only could have done if he used his ID card to unlock the door to the cell. (28 Weeks Later)
The Infected prefer to be in shaded to pitch black areas compared to bright light. For example, the survivors of the Original Outbreak would rather move during daylight, the Infected which chased Jim, Hannah, Frank and Selena through the underground tunnel in London did not not follow them into the daylight, and the Infected which attacked the Worsley House usually only did so at night. (28 Days Later (film)) Also, those among the Infected from the Second Outbreak which survived the Code Red firebombing were shown to retreat into the Underground at dawn. (28 Weeks Later)
It has been shown that when an uninfected individual is near, an Infected will become enraged and try and get to, and infect or kill the uninfected. However, those infected with Rage will also ignore each other, only attacking those who are not infected and/or do not show symptoms of Infection. The Infected use their sense of smell (which is apparently enhanced by Rage and/or the immense rage the disease causes) to find the uninfected and to tell other Infected from the uninfected, and trace amounts of products such as perfume or soap will attract the Infected to the source. (28 Days Later: The Aftermath)
But once the uninfected has gone and the Infected is unable to go after them, the Infected will give up and probably go in search of other victims. (28 Days Later (film), 28 Days Later (comic series)) If Infected hear a sound made by uninfected, they will relentlessly search the source of the sound for the uninfected; but if they are unable to find them quickly enough, they will quickly abandon searching for them and go back to searching for other victims. Also, if one Infected hears a noise and begins attacking a vehicle or a building to find the uninfected inside, other Infected who notice this will see that the Infected has found uninfected people, and will join in the attack. (28 Days Later (comic series))
It would appear that the Infected may be more aggressive and vicious towards Carriers than they are towards victims who are susceptible to Infection. This is most likely because Carriers cannot become Infected due to their immunity to the symptoms of the Rage Virus. After Don Harris was infected, he brutally and savagely attacked, mutilated, and killed his wife Alice (who was a Carrier). However, it has also been suggested that this was not because she was a Carrier, but because of Don's memories of her. (28 Weeks Later)
The Infected still have the same level of, if not increased, mobility as they did before becoming infected. It has also been shown that they do possess a rudimentary sense of spatial awareness; for example, the infected Donald Harris was shown to be able to manipulate such simplistic objects as blunt-force weapons. The Infected can be killed by conventional means, though killing an infected human may be made more difficult by their adrenaline enhanced strength, endurance and disregard for pain. (28 Weeks Later) The Infected also gain a heightened sense of smell from the Infection and/or their own extreme rage. (28 Days Later: The Aftermath)
The Infected are extremely sensitive to light, as the light of one small candle was shown to be sufficient enough to draw the attention of nearby Infected; (28 Days Later (film)) and the infected Don Harris had little trouble roaming around in the abandoned Underground, whereas Tammy, Andy and Scarlet Levy needed night vision in order to navigate through the darkness. (28 Weeks Later)
While the Infected do eventually die from lack of nutrition, they seem to be able to last longer than uninfected individuals without nutrition, to the point that the Infected can last for up to eight weeks or less before becoming too weak to move. (28 Days Later (film), 28 Weeks Later)
Rage does not directly cause the death of its host, but because the host is solely focused on infecting or killing the uninfected, it causes those infected to become disinterested in self-nourishment, which will eventually cause death by starvation. Also, as the Rage Virus causes its hosts to act with no regard for self-preservation, the Infected will not act to evade mortal danger, such as fire, gunshots, or chemical gas. Though the Infected possess a disregard for pain, the number of major body parts severed will affect their mobility, as one Infected was shown to move very slowly compared to other Infected after its arm and shoulder were severed by helicopter blades. (28 Weeks Later)
It has been shown that the Infected cannot swim, as while they can run through shallow waters (such as waters that are three or four feet high), (28 Weeks Later) if they run into deeper water, they will get caught in it and drown. (28 Days Later (comic series))
Differences from zombies
The Infected are distinct from cinematic zombies in that they are living people infected with a virus that induces intense, single-minded rage and aggression, and not the reanimated dead. Also, films such as George A. Romero's Living Dead series, Return of the Living Dead, and the Resident Evil series portray zombies as creatures that desire to consume living flesh. By contrast, while the Infected will attempt to bite their victims, it is usually as a means of either killing them (often by severing the main arteries in their neck) or spreading the Infection. They are not shown to ingest any organic material, apparently due to said disregard for nourishment.
Another key difference is that the Rage-infected victims are still living human beings and as such can be killed by weapons and other means that are fatal to uninfected humans. (28 Days Later (film), 28 Weeks Later, 28 Days Later (comic series)) Also, while the standard cinematic zombie is depicted as a slow and clumsy creature, the Infected are very strong and fast-moving, thanks to their adrenaline-enhanced stamina. Unlike other zombies, the Infected, while losing most of their higher levels of intelligence, are apparently highly attuned to their surroundings, being able to navigate over and around obstacles to otherwise unseen targets; (28 Weeks Later, 28 Days Later: The Aftermath) whereas most other zombies will simply try to approach uninfected individuals from the most direct route, often failing repeatedly. The Infected in a similar situation will simply run into the building, often destroying doors and windows, and go through the structure to reach the designated target. (28 Days Later (film))
- Ethan Van Sciver, Green Lantern writer and artist, officially stated in Issue #2 of Blackest Night: Tales of the Corps that the Red Lanterns, people that wear red power rings, are filled with rage and spew dangerously acidic blood, were inspired by the Infected from the 28 Days Later franchise. He also mentioned that they were his favourite Lantern Corps.
- The Flood from the Doctor Who episode The Waters of Mars are similar to the Infected in that they are both humans infected with an extremely virulent and fast-acting virus, and both produce copious amounts of infectious blood/water from their mouths.
- People who are observant will noticed that the Infected sometimes go after their former friends or family (now turned enemies). Examples of this are:
- The only infected animals to be seen (so far) are the chimpanzees from 28 Days Later; apart from that no other infected animals are seen. Oddly, there does not appear to be that many animals seen in Britain since the Original Outbreak occurred (though there are still some horses, swans, deer, crows, pigeons, rats and dogs). However, it is probable that most of the animals in Britain were killed by the Infected due to their fits of rage and/or due to the fact that only primates (such as humans and monkeys) are able to carry the Rage Virus. It is probable that if an animal was exposed to the Infection, it would be unaffected, as Rage can only use primates as its hosts.
- The Infected seen in 28 Weeks Later are apparently as active during the day as at night, forcing survivors to take cover in the darkness. But in 28 Days Later and the comic series, the Infected were much more active at night than during the day. The reason for the Infected in 28 Weeks Later being diurnal is not explained anywhere, and it could have been overlooked, or it could just be the Infected's sheer determination to find more uninfected victims. Another possibility suggested by a few fans is that people infected do not become nocturnal until some time after infection. This is supported by the fact that most of the Infected seen in Days and the comics had presumably been infected for weeks, whereas the Infected encountered in Weeks had only been infected for hours or days at the most.
- The Infected appear to have a slower metabolism than normal, being able to last for weeks or even months before succumbing to starvation. However, considering the amount of adrenaline the Infected use to try and infect or kill the uninfected, this should be the other way round; their metabolism should speed up rather than slow down. This could mean that the Rage Virus alters its hosts' metabolism to make them last longer than normal without food or water.
- It is debated whether or not the Infected speak verbally, as in 28 Days Later, an Infected Child yelled "I hate you!" at Jim before the latter killed him. However, Danny Boyle confirmed that the child speaking was due to an audio inconsistency. It is believed that the Infected do not speak, as in the 28 Days Later comics, Gordon and Luis Rodriguez both told survivors from Infected by seeing whether or not they spoke.