After the war, the scientists within Vault 22 conducted agricultural-based initiatives, with the goal of sustaining the Vault population with plants grown within its confines.[Non-canon 1] Designed as a green Vault, people selected for populating it were dedicated to goals surrounding plant life and crop expansion. One of the experiments revolved around Beauveria mordicana, a fungus designed for pest control. The Vault scientists began experimentation, it became airborne. Fungal spores gradually spread through the Vault, infecting the population.
After several inhabitants became sick with a pronounced cough, scientists were confused and attempted to pinpoint the cause. The first confirmed infection and fatality was Dr. Harrison Peters. The subsequent reanimation of his corpse frightened and bewildered the scientists, who attempted to contain those who were ill. When exposed to B. Mordicana spores, the host is slowly overtaken by the fungus. The affliction kills within 10 to 20 days, but the pathogen within continues to thrive, causing reanimation to occur. In response to the outbreak, the remaining scientists attempted to eradicate those who had reanimated by releasing and then igniting gas in the lower levels of the Vault. This triggered a defensive reaction from the carriers, who attacked the scientists.
A group of Vault 22 survivors, numbering more than one hundred, organized an expedition to Zion Canyon in 2096. Many members of the group were infected by the Beauveria mordicana, and would eventually succumb to become spore carriers.
Spore carriers can also be found in the X-22 botanical garden in Big MT, the source of the Beauveria mordicana used in Vault 22's experiments. A unique spore carrier named Patient Zero, implied to be the first of its kind, still roams the facility.
Spore carriers are quick and use melee attacks. If they are not killed quickly, they explode and deal large amounts of damage, breaking limbs and giving a large dose of radiation. When they are hiding in vegetation, they are hard to spot and will not appear on the Courier's compass, nor be targeted via V.A.T.S. until they move.
However, their health meter will become visible if they are injured by an area-of-effect weapon, like a flamer or grenade, immediately revealing their presence. While a spore carrier is getting up or sleeping, attackers in sneak mode who manually attack the spore carrier will receive a critical.
The most common of all spore carriers. They hide in vegetation.
↑The Courier: "How did you get this whole gas thing set up so quickly?" Keely: "That's a very good question! Actually, I didn't come up with it. The systems were already set up to pump the gas when I first arrived here. I believe the scientists were in the process of attempting to ignite the gas just as we're about to do. And by we, I mean you, of course." (Keely's dialogue)
↑The Courier: "What happened to the scientists, then?" Keely: "Something prevented them from igniting the gas, obviously. I suppose it's possible that the gas triggered some kind of defensive reaction. Hordes of previously slumbering creatures may have awoken and entered a killing frenzy, ripping the hapless scientists into quivering, bloody chunks. You'll have to let me know when you get back from going downstairs." (Keely's dialogue)
↑Old World Blues endings: "The Biological Research Station, obsessed with seeding everything in sight, requested a transfer to the X-22 Botanical Garden... so that it might, in its own words, "sensually fertilize the garden's smooooth contours." The Garden sent back a polite refusal, saying it had prior commitments with a Vault it had helped infect before the war.
↑Fallout: New Vegas Official Game Guide Collectors Edition pp. 292-294: "[1.09] Vault 22" "Vault 22 was a "green" vault, filled with scientists dedicated to their experiment: keeping the entire population of the vault alive with plants grown with its confines. The experiment could be said to have exceeded all expectations, but with horrific side-effects. Many have attempted to locate the data the scientists left behind, but so far nobody has returned alive. The vault is open, but warning signs surround it from people lucky enough to survive their initial encounter with the vault's inhabitable. Don't forget to check the Hollowed-Out Rock on the right side of the gully, across from the "Keep Out!" sign." (Fallout: New Vegas Official Game Guide Collector's Edition Tour of the Mojave Wasteland)