'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 ten to twenty seconds. Symptoms include constant spasming, and internal bleeding from all bodily orifices as well as haemoemesis (vomiting infectious blood). Usually, the Infected exhibits no goal or trace of their former-selves and will not hesitate to attack former loved ones (Donald Harris was a notable exception who experienced fragment memory flashbacks, although it did nothing to curb his aggression and seemingly motivated him further to attack his loved ones). The Infected individual is driven by 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 (at least not when they are in pursuit of uninfected), although it's implied they fled the fires in Manchester.
Due to the virus' easy transmission, very short incubation stage and the extreme effectiveness of the rage-fuelled, mindless vectors; a single Infected can induce a severe domino effect in crowded areas, causing the Infection to spread like wildfire as the Infected rapidly multiply. However, the Rage Virus' aforementioned strengths also count as weaknesses alongside its inability to infect non-primate hosts, as they prevent the Infection from being easily or unintentionally spread overseas beyond a populated island.
A human, chimp or other primate that is exposed to the Rage Virus through bodily-fluid contact of blood and/or saliva - a bite, a kiss, an injection, or infected blood getting in their eyes or mouth - will become Infected in between ten and twenty seconds. The onset of Rage during this period is marked by painful, uncontrollable convulsions and spasms in the extremities, bleeding from the eyes, and seemingly a rapidly-building increase in anger in the host (28 Days Later (film), 28 Weeks Later). Once a victim is exposed, it would appear that the amount of time it takes for the Infection to fully infect them 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 he began to show onset symptoms, 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 near-constant spasms in their extremities, (28 Days Later (film)) and their irises enlarge and become bloodred. 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 of the capillaries (28 Days Later (comic series)).
While the Infected do eventually die from effectively starving themselves to death, they seem to be able to last longer than uninfected individuals without nutrition, as it took until four weeks after the Original Outbreak's twenty-eighth day before the majority of the Infected in England became too weak to move, whilst there were still many Infected in Scotland months later. (28 Days Later (film), 28 Weeks Later)
Intelligence and behaviour
The Infected seemingly retain basic problem-solving intelligence. They have been known to instantaneously disregard uninfected they were attacking or pursuing if they abruptly die before the Infected can infect them; as was seen during the Second Outbreak, when an Infected immediately tossed aside a woman it had grabbed when a sniper shot her, and when two Infected who were in the process of mauling a sniper instantly fled when the sniper was killed by a headshot. (28 Weeks Later) The Infected are shown to retain some spatial awareness, as they can calculate complex routes to unseen targets. They 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 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 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 - Hugh Baker speculated that Infection (as with other diseases) or even just the all-consuming rage it induces could've enhanced the Infected's sense of smell. (28 Days Later: The Aftermath)
The Infected prefer to be in shaded to pitch-black areas compared to bright light. In the direct aftermath of the Original Outbreak, numerous different survivors considered it safer to move at day than during night, when Infected were shown to emerge into the open (28 Days Later (film), 28 Days Later (comic series)); the Infected which chased Jim, Hannah, Frank and Selena in an 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)) Those Infected from the Second Outbreak which survived the Code Red firebombing were shown to retreat into the Underground at dawn. (28 Weeks Later) However, the Infected are by no means solely nocturnal - the survivors at Geoff and Sally's farm were forced to fortify against Infected that were active during the day, and the sunrise following the Second Outbreak didn't prevent a massive horde of Infected approaching Regent's Park. Infected have been observed to, when inactive, simply lie amongst corpses before being alerted to the presence of uninfected, seemingly sleeping until noise jars and alerts them. (28 Days Later (film), 28 Days Later (comic series))
Infected may give up a chase and go in search of other victims if they're unable to reach an uninfected due to physical barriers - but this isn't likely to happen, due to the Infected's rabid motivation and physical capabilities making them very unlikely to give up. (28 Days Later (film), 28 Days Later (comic series)) 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. (28 Days Later (film)) When Don Harris closed and locked a door between himself and an Infected, the Infected spent roughly four seconds attempting to break the door down, before giving up and turning its attention (along with the other present Infected) to attacking two other uninfected who were immediately behind it instead. (28 Weeks Later) When in pursuit, Infected will not act to evade even oncoming mortal danger such as fire, gunshots, chemical gas and sharp weapons. However, it's implied Infected might act to preserve themselves at other times, as the fires which destroyed Manchester drove hundreds of Infected into the surrounding countryside.
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. It's also been observed that when one out of numerous Infected senses a sign of uninfected activity and attacks the source, other Infected will take note of the commotion and join in the effort. (28 Days Later (comic series))
After being infected, Don Harris exhibited unusual levels of intelligence that were usually devoid in the Infected; he apparently had fragment memory flashbacks (if not complete memories) of his family when in their presence, which seemingly motivated him to pursue and attack them. 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. A further show of his intelligence was his use of an M4 rifle as a blunt-force weapon to beat Scarlet Levy to death. (28 Weeks Later)
Little is known about how the Infected would react to Carriers and if it would be any different than how they react to uninfected, in a standard situation. Only Don was ever known to interact with a Carrier (his wife after being unknowingly infected by her), and his reaction may have been due to his aforementioned flashbacks while infected - upon recognising his Carrier wife, he proceeded to savagely attack, mutilate and kill her. (28 Weeks Later)
The Infected possess a seemingly adrenaline-heightened mobility, with Don Harris noting they were very fast-running when recalling his escape on foot from them - indeed, despite Don's own adrenalised mobility, the Infected gradually closed distance behind him over their field-wide chase (28 Weeks Later). In spite of their adrenalisation and single-minded rage, Infected have been known to ignore or quickly shrug off pain and injury that would be debilitating if not outright fatal to people under normal circumstances; such as gunshots to body-parts that don't instantly kill them, dismemberment, and being burned alive (28 Days Later (film), 28 Weeks Later, 28 Days Later (comic series))
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)
The Infected's aforementioned durability and disregard for harm to themselves makes them difficult to slow down or even disable with means that would usually literally or figuratively cripple a person (such as fire and gunshots). However, the number of major body parts severed will affect their mobility despite their disregard for it, as one Infected moved very slowly compared to other Infected after its arm and shoulder were severed by helicopter blades. (28 Weeks Later)
The Infected apparently 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))
Rage does not directly cause the death of its host, but because the Infected don't actively seek self-nourishment, they effectively all have a limited lifespan before they weaken and finally die from starvation.
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 but wouldn't destroy undead zombies. (28 Days Later (film), 28 Weeks Later, 28 Days Later (comic series)) While the standard cinematic zombie is often depicted as a slow and clumsy creature, the Infected are very strong and fast-moving, thanks to their adrenaline-enhanced stamina. Unlike most 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.