The superheroes of the Marvel Comics universe have had to deal with a multitude of threats since their stories began to unfold. Galactic warlords, alternate realities, sadistic murderers, and alien races have all been responsible for some of the biggest dangers to Earth-616, but there have also been a fair few silent killers too.
Viruses have killed off a lot of heroes, and caused others to suffer some hideous transformations, so we thought it only right to look at the 10 deadliest viruses in Marvel's history. Whether they've affected a handful of people or an entire civilization, these biological hazards have been a monumental threat to many of our favorite characters.
10 Virus X
The Mental Organism Designed Only for Killing (or MODOK for short) started out as a technician for A.I.M., but after becoming too ambitious for his own good, he ends up killing his former scientist buddies. In Marvel Two-In-One #81, he tests out a deadly virus known as Virus X and shows the world just how evil he can be.
The Thing is infected by it, and begins to mutant into a more hideous version of himself. After an antidote is eventually found, Giant-Man decides to use it to cure Ben Grimm, even though he could have used it on himself to rid his body of the cancer he has. Whilst it didn't infect a lot of people, its affects on the Thing were never pleasant to see. Thanks to Bill Foster's help, he was restored back to normal.
9 HX-N1
Created by Lobe of the Sublime Corporation, Contagion X - or HX-N1 as it was also known - was a synthetic virus capable of weakening a mutant's power, rendering them useless. It showed symptoms familiar to influenza, and had the ability to show affects within hours due to the nano-machines able to replicate the viral structure.
Wolverine and Magneto were just two of the mutants affected, with the former gaining blood poisoning due to the adamantium attached to his skeleton. When Lobe was infected by the disease it gave him mutant abilities. As a way to rid himself of the virus, he managed to save himself as well as creating a cure for the mutants who'd been infected.
8 Extremis Virus
FuturePharm was a subsidiary of Stark Industries, and it was there that Extremis was created. It was a type of Super Soldier serum invented by Dr. Aldrich Killan and Maya Hansen, giving those infected superhuman abilities. A villain known as Mallen was infected by Extremis, but was killed by Iron Man.
The fact that the drug could give normal individuals untold power became a worry for Iron Man, as one of his greatest enemies, the Mandarin, wanted it for himself. It messed with natural evolution, and could prove deadly if in the wrong hands. With great power comes great responsibility, but those that used it weren't always responsible.
7 Ultimo Virus
Ultimo was an enemy of Iron Man, created by an alien race he ended up destroying. Using the remains of the giant android, Dr. Phillip Prometheus created the Ultimo Virus, which could transform anyone infected into superhuman versions of themselves.
Be it animal, plant, cyborg, or human, the virus implants similar traits of the murderous machine, such as healing abilities, laser vision, and super strength and speed. It's so strong that it can even affect Gods, such as the time it infected Ares, but thanks to the joint efforts of War Machine and Iron Patriot, it was stopped from doing damage to Earth's population.
6 Reaver Virus
Created by Kirk Jansen, the Reaver Virus turned anyone infected into dangerous cyber-organic threats. Their main goal was to murder mutants, as Magneto discovered in X-Men Blue #33. Upon visiting a post-apocalyptic future where most of mutantkind had been killed as a result of the spread, he returned to the present with the intent of killing the scientist responsible.
It was never intended to take on the form it did, but hatred was the cause for its spread. Magneto often walks a line between good and evil, and is at his best when he is pushed to meander through the two pools of conscience at each end of the spectrum. This storyline is one of his finest, and it brings about one of the most destructive viruses there is.
5 Hunger Virus
A Sentry infected with the Hunger Virus was sent to Earth-2149 by the Watcher, and it quickly turned everyone into zombies. Much like every famous version of the undead in comics, movies, and video games, the virus was spread via biting, and it caused every superhero to turn into a flesh-eating monster.
Heroes with accelerated healing abilities would still be susceptible, but it would take a little longer. Ultimately, though, when the process was complete, no living soul was safe. It infected the world within 24 hours, and the likes of the Fantastic Four, Spider-Man, Captain America, and Iron Man would all become victims of the Hunger Virus.
4 Carrion Virus
Like the Hunger Virus, the Carrion Virus messes with the host's brain and begins to degrade their psyche, ultimately turning their brain to mush. They become enraged and psychotic, breaking down their cells and causing their bodies to stop functioning. Although there isn't a cure, it can be controlled by the consumption of a pill.
In Earth-616, it was created by the Jackal to cause untold devastation in Manhattan, but thankfully Spider-Man and the Scarlet Spider managed to stop it. Another version of it infected different universes and was the result of both New U Technologies and Parker Industries coming together to use cloned body parts for organ transplants.
3 Ultron Virus
Anyone who has heard of Ultron knows exactly how evil the sentient A.I. is. Created by Hank Pym, Ultron soon became a weapon of ultimate destruction, and the Ultron Virus was a tool used to transform anyone it infected into another version of the vicious machine.
Once it latches on to its host, it takes over and turns them into another version of Ultron, harboring the same murderous tendencies and hatred that Ultron is capable of. Every thought and feeling Ultron has is instilled in anyone infected, creating an army of Ultron Sentinels capable of replicating his evil ways, driven to infect more people with the virus.
2 Transmode Virus
The Transmode Virus has the ability to turn living tissue into technology, creating techno-organic cells to function like individual machines that store every bit of information on their carriers. This way, a single cell can rebuild the host if needed. Infected individuals can end up becoming one of the Phalanx - a cybernetic species created by the Technarchy.
The Technarchy are a race of aliens (the most famous members of the species being Warlock and Magnus) that can shapeshift, who scour the universe looking for beings to infect with the virus so they can then feed on their energy. There was another variant of the virus used by Apocalypse, who managed to infect a young Nathan Summers. This led to his teleportation to the future, and so his becoming Cable.
1 Legacy Virus
Perhaps one of the most famous viruses within the pages of the Marvel Comics Universe, the Legacy Virus caused untold destruction to many mutants. It was created by Cable's evil clone known as Stryfe - a mutant from 2,000 years in the future. The virus devastated many mutants, including Colossus' younger sister Illyana.
There are three versions of the virus, each one triggering when a mutant would use their powers after first contracting the disease. It has returned over the years in the comics, but the most famous version of it was wiped out when Colossus sacrificed himself to save all mutantkind. Although his death was upsetting, it did create a cure to the original virus.