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See also: Type-2 Plagas and Type-3 Plagas

Las Plagas (a Spanish word translating literally to "the plagues") are a species of parasitic organisms. Unlike the t-Virus, which turned its victims into mindless zombies, the victims of Plaga (such as the Ganado and Majini) become much stronger and highly resistant to pain, while working collectively to pursue their targets. Other side effects include complete loss of higher reasoning - except in select subjects (who remain unable to resist the need to obey higher orders) - and full compliance to the Dominant Species Plaga.

Resident Evil 4 - Las Plagas 1

Plaga parasite replacing the head of its host


The Plaga were first discovered by a religious group in Europe known as "Los Iluminados" (The Enlightened Ones) in an unknown, rural region of Spain. The cult used the Plaga as a means of recruiting new members; however, the first castellan of the Salazar Family opposed the cult and sealed off access to the parasites in his castle.

Centuries later, Ramon Salazar, the eighth Salazar castellan, was convinced by Osmund Saddler, the new leader of Los Iluminados, to join Los Iluminados and break the seal that contained the Plaga. The two hired the local villagers as miners to extract the parasites.

Fossilized Plagas

Fossilized Plaga

Due to years of confinement, the Plaga parasites initially seemed dead. Some were later found fossilized (which normally takes millions of years) in the rocks below Salazar's castle. However, despite this, there were still living Plaga spores within the fossils. The miners that were hired to excavate the parasites inadvertently inhaled these spores, allowing the Plaga to grow within them. Since then, Saddler was able to recreate the parasites wholly, injecting them in egg form into potential hosts.

Leon, Ashley, and the Third OrganizationEdit

The 3rd Organization learned of Plaga some time in 2004 when Ada Wong intercepted a desperate phone call from Saddler's chief researcher Luis Sera. Albert Wesker tasked the rogue former-US-SOCOM operative Jack Krauser to infiltrate Saddler's inner circle in the hopes of acquiring a Plaga specimen. Although not trusting Krauser, Saddler gave him a Dominant Species Plaga in exchange for Krauser's assistance. Saddler wanted to acquire Ashley Graham, daughter of the US President, in order to turn her into a host for the parasites and subsequently infect her father upon release. This was Saddler's ultimate goal for world control, with the president under his command. Krauser, as an American who had worked on Government missions before, was considered the perfect abductor for Ashley.

Saddler killed Sera, and Leon fought and supposedly killed Krauser and chased down Saddler. Krauser is shown to have actually survived his defeat but is killed by Ada soon after. Leon found Ashley and proceeded to defeat and kill a transformed Saddler and recover the Dominant Species Plaga, only for it to be taken from him by Ada at gunpoint. Leon and Ashley then escaped the self-destructing island via Jet-ski.

Ada betrayed Wesker and gave him a normal subordinate Plaga, delivering the Dominant Plaga sample to a different organization she was actually loyal to. Wesker later retrieved a sample of the Dominant Plaga from Krauser's corpse.

Uses in bioterrorismEdit

Five years later, within the African country of Kijuju, Chris Redfield and Sheva Alomar soon encountered Plaga-infected villagers. These Plaga were modified through intensive research to enhance their performance and create more effective B.O.W.s.

During the Eastern Slav civil war, Lickers were used as Plaga hosts, bringing them under the control of those carrying the Dominant Species Plaga. The secessionists required multiple Dominant Species Plaga, as their chosen council leaders eventually lost control to the parasites and had to be killed. During the same conflict, submissive-strain Plaga were somehow released and began infecting loyalist soldiers, secessionist rebels and civilians indiscriminately, creating infected humans that, while called Ganado by the locals, were more like the Majini of Africa. The loyalist government was also eventually revealed to be cultivating Dominant Species Plaga of their own.


Plaga are a type of parasite which alters its host's behavior by attaching itself internally to the nervous system. The undeveloped parasite is found between the lungs, beneath the heart, where it can tap into the host's spinal cord, as a link to the rest of the nervous system. Unlike other parasites, the Plaga are a social organism, meaning that they live together in social harmony. Luis Sera postulates that they have a collective intelligence akin to a hivemind, possibly communicating via ultra high frequency sound waves. Even when unhatched, the Plaga do demonstrate some symptoms in the host, like turning the eyes red briefly.[notes 1]

As a Plaga grows inside a host, the host can suffer from a number of symptoms (in addition to the influence of the parasite on the host's behavior). These include, but are likely not limited to: coughing up blood, blood flowing from the eyes, convulsions, sudden unconsciousness, hallucinations, swelling and discoloration of blood vessels, and discoloration of the iris – usually to a reddish color. The eyes of an infected person can be seen to glow in dark conditions.

The parasites also have a high adaptability rate, as they can possess other organisms than humans. (Ramon Salazar uses Plaga-infected wolves as guard dogs in his castle.) In addition to the Ganado, Saddler and his men also created several kinds of mutant creatures such as the El Gigante, the Regeneradores/Iron Maidens, Novistadores, the U-3, and Salazar's bodyguards, the Verdugos, as a result of genetic experimentation with the parasites and human specimens.

All of the members of Los Iluminados, including Saddler himself, have Plaga parasites implanted into their bodies. However, the ones used by him and his top underlings (Bitores Mendez, Jack Krauser, and Salazar) are superior to the regular Plaga, allowing their host a greater amount of independence.

Except for manifesting when sufficient trauma is induced on a host, Plaga have no true mutagenic effect on their hosts' body other than the distinctive red irises. While the Plaga infecting the Ganado and Colmillos can manifest and mutilate the body of their host, they do not actually induce any significant mutation or physiological change like Umbrella's myriad viruses do. However, certain feats by enemies in the game (such as lifting Leon into the air with one hand) suggest that the parasites can increase their hosts' strength. It is the fact that hosts exhibit no outward sign of infestation besides discolored irises that make the Plaga such a dangerous threat, as they are much more subtle and invasive than Umbrella's viruses. The Plaga parasite does not stop their hosts from feeling pain however, unlike the t-Virus zombies, since the hosts have still retained their nervous system. Rather, they give their hosts better resilience against bullet wounds. Plaga are, however, weak towards UV light, although Dominant Strain hosts seem to be either immune or more resistant towards it, as evidenced by Saddler fighting Leon in the former's Plaga form during daybreak.

Also of note, according to a note written by Saddler, the subject's mindset does seem to be important when choosing a host ("the Plaga reflects the conscience of the hosts") suggesting that a Plaga's control over the host can be resisted, even overcome entirely. This seems to be a reference to Sera, who was a host himself before managing to remove his Plaga. This might also explain the need to kill those who refused the Plaga, as they were obviously judged to be "incompatible". It also seems to be a literal description as well, at least in the case of the Dominant Species Plaga, as Krauser, who preferred close combat, developed a bladed arm to suit his needs. In extremely rare cases, the Dominant Species Plaga will also create a far larger body while the host itself is connected to a cocoon-like membrane. This is especially apparent with Ramon Salazar and Ricardo Irving's transformations (although the former was due to fusing with his remaining Verdugo guard and the Queen Plaga instead of using his own Plaga directly), and to a lesser extent Osmund Saddler's transformation.

Another side effect viewed in those infested with Plaga is an apparent biological instability, as seen in that they disintegrate into a black or yellow goo when killed. This is common with nearly all Plaga infested individuals, including both Majini and Ganado. However, certain individuals, such as the first group of Ganado that Leon encountered in Resident Evil 4 and minibosses, do not disintegrate when killed. The Plaga themselves, for the most part, also suffer the same fate upon death. However, there are some cases of the Plaga itself remaining intact after death.[notes 2]

In the game, the Plaga of the Ganado, Cultists, and Combatants only appear where the head is. Once a Plaga is exposed, the enemy will no longer sprint towards the victim.

The Majini located within Kijuju are infected with a different type of Plaga, created through extensive research. The Majini have been shown to develop strange mutations, such as tentacles within their mouths, as well as the ability to fully open their mouth/jaw to expose tendrils to attack others. It has also been shown that the Plaga within Kijuju appear to already be fully awakened, and enter via the mouth or throat, already hatched. They seem to grow inside the host of another Plaga, which will later transfer them to other possible hosts, eliminating the need to inject the egg. These Plaga also do not appear to be harmed by sunlight, as they appear within brightly lit areas. Some strains have also been shown to fly after leaving the host body. Despite these new modifications, they are still vulnerable to the bright flashes of flash grenades (i.e. UV light).

Plaga SpeciesEdit

Subordinate-strain Plaga - These are the normal Plaga species. They have no individual form by nature and it is not certain what dicates their manifestations.

Dominant Species Plaga - These are the complex types of Plaga which were genetically modified in order for the host to retain control. They have three distinct abilities which separate them from Subordinate Plaga - they allow the host to retain their free will, control other Plaga, and cause dramatic mutations in their host at will. They are opposite of the Subordinate Plaga, and allow the host to exert complete control over the parasite. The only known subjects to have ever been infected with this Plaga were Osmund Saddler, Bitores Mendez, Jack Krauser, Ramon Salazar, Ricardo Irving, and Alexander Kozachenko. Notably, this type of Plaga can create extremely powerful individuals, while having almost no detrimental effect on the host's mental capacity; something Umbrella's top virologists failed to manufacture.

Plaga Life CycleEdit

Once it hatches inside a human host, the larval Plaga undergoes three primary stages of development.

  • Plaga A[1] - This is the first form of Plaga that Leon will encounter. Their bodies are pulsating masses of flesh and waving tentacles, with the longest tentacle armed with a scythe-like blade that can slash at the player from a decent range, and also while they are knocked on the ground. They are the weakest of the Plaga species and can be killed with minimal effort. Type A Plaga are commonly found in Villagers and Militia, and also control the weaker Armadura suits.
Resident Evil 4 - Las Plagas 1

Las Plagas parasite replacing the head of its host


Plaga B, erupting from a zealot's head.

Plaga Infection

Plaga C

  • Plaga B [1] - These Plaga are the second form of Plaga that Leon will encounter infesting human hosts. They are often found inside the lower-ranking zealots, and are the second type which control Armaduras. This version of the Plaga can extend its entire body (being the Plaga itself) towards Leon and it will devour his head—an instant kill. The B-parasite is capable of no other attacks. It is at a high risk that you should ever get close to this Plaga due to its one-hit kill effect. While not advisable, it can be killed with a knife. Interestingly, this type of Plaga does not destroy the host's head or body when revealing itself. As with the type A Plagas, it can be killed using a flash grenade.
  • Plaga C - These Plagas mostly inhabit the higher ranking zealots and militia. They are the most durable, can spit acid from some distance, and detach themselves from their host following death. They are roughly equal to the A-parasites in terms of threat while attached, and are relatively weak when detached. While detached, they have a leaping grapple which lacks an animation for attacking from the side or rear, much like the Colmillos, meaning they can only use it when directly in front of Leon. Curiously, several are encountered in the game without hosts at all, such as in the case of the battle with Salazar. When without a host, a C-parasite will eventually die, even if it has taken no damage from the player. As they can't climb ladders, simply moving outside their immediate area is an effective way to kill them.

Alternate Plaga ManifestationsEdit

  • Leech-like Plaga - When multiple Plagas are inserted into human hosts, they cause the host to undergo drastic physical mutations and become more leech-like in appearance. They are capable of regenerating the host's body (Regeneradores).


The Plaga are very vulnerable to bright light. They will only emerge from their hosts at night (except in The Mercenaries), and can be instantly killed by throwing a Flash Grenade at them (except for Spider Plagas that are attached to a host; with these, a flash grenade will dislodge them from their host, while it takes a second to kill them).

A weapon called the Plaga Removal Laser 412 (P.R.L. 412), which is unlockable after completion of the Professional difficulty, can instantly kill any enemy infected with Plaga. It is presumably a weaponized version of Luis's machine.

The kind of radiation the Plagas are weak to seems to be UV light, since most lights used to destroy it are colored blue/purple, meaning that they emit enough UV light. Another possible explanation for their photosensitivity is that they may react to a certain level of Candela (meaning that the brighter something is, the stronger it is against the Plagas).

Known treatment Edit

Only a dormant Plaga can be treated, as type 2 and type 3 infect the host too fast. Therefore, making treatment with these type of Plaga impossible without killing the host.

Suppressor Edit

If a person has become the host of the parasite, the parasite's growth can be suppressed by taking medication. These special pills are produced by Luis Sera, a researcher who betrayed Saddler.

Radiation Treatment Edit

However, once the Plaga has hatched, then the only way to terminate the parasite without killing the host is for them to undergo a special kind of radiation treatment.[2] This extremely painful procedure has the possibility of impairing the host's consciousness, and may still kill the host if the Plaga has already matured into adulthood.

Luis Sera also designed a machine which produced this kind of radiation after extensive research regarding how the Plagas might be removed. Ironically, he was tasked with finding a way to prevent any form of removal of the parasite by Saddler. Leon and Ashley, who had Plagas implanted into their bodies, used the machine to eliminate the Plagas, with both managing to survive the operation, as the Plagas had not reached their adult stage.

Direct Damage Edit

Although killing a Plaga once it has bonded with a human's central nervous system is likely to result in the death of the carrier, it is possible to kill the Plaga once it has bonded with a human's spine without killing the host. However, it will result in the individual being permanently paralyzed from the waist-down for the rest of their life. This was especially notably seen in the Eastern Slav resistance member, Buddy.

Further NotesEdit

  • All lower level Ganado are shown to have lost their need for personal hygiene, due to the observations Leon makes in the first few chapters of the game and various water sources throughout the game.
  • The B-Plaga is the only of its kind (human host Plaga) that can perform an instant death attack, by literally biting Leon's (or any other of the Mercenaries in the mini game) head off. This Plaga can also kill Ashley, having the same "head eating" animation, but would just hit her, making her fall lifeless in the floor.
  • Plaga can be compared to crimson heads, because they appear after an organism's supposed death, and make the creature even more fierce.
  • In Resident Evil: Damnation the Licker becomes infected with a new parasite[citation needed] that allows it to be controlled by anyone who is infected with a Master Plaga sample.


  1. When Mendez ambushes Leon in the hallway of his house, Leon's irises when struggling against Mendez's strangulation of him briefly turned red, which led to Mendez deducing that Leon "carried the same blood" as the Los Illumnados. This occurred before the eggs hatched.
  2. Albert Wesker managed to retrieve an intact version of the Dominant Species Plaga via recovering and autopsying Krauser's corpse, and supply it to TRICELL for mass-production.
  1. 1.0 1.1 Biohazard 4 Kaitaishinsho Katei Ban, page 92
  2. Re'sident Evil 4, Luis' Memo 5


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