Cordyceps Brain Infection (Earth-96)

"It forces its way into your mind... your soul... you can't fight back."

- - Ethan Winters The Cordyceps Brain Infection, shortened CBI, is a parasitic fungal infection that has devastated mankind in 2017, drastically reducing the world's population in 80%, with fifty million of humans left alive in the globe.

The infection began to spread in late September 2017. In just several months, roughly 30% of humanity was either killed or infected by the cordyceps fungus, and in five years, 80% of humanity had already perished.

Stages
The fungus grows while the host is still alive, taking away their higher brain function (and with it, their humanity), and causing the infected host to become hyper-aggressive and incapable of reason or rational thought (Stage 1); Stage 1 starts anywhere in between 1-2 days of infection.

As the infection progresses, the infection begins altering their sight as a result of progressing fungal growth over the head and corruption of their visual cortex (Stage 2),; Stage 2 starts anywhere in between 1-2 weeks of infection.

The infection will eventually scar their face completely, causing them to lose their sight, resulting in them developing a primitive form of echolocation to compensate (Stage 3); Stage 3 starts anywhere in between 1-2 years of infection.

Over a very long time, they will eventually develop hardened fungal plates over most of their body (Stage 4), Stage 4 starts anywhere in between 1-2 decades of infection. If the fungus kills the host, the host's body will grow stalk-like fungal projections which release infectious spores.

The infection can also be spread through bites from living hosts. Hosts can only be infected while alive, as the fungus is unable to infect dead bodies due to it's parasitic nature, though dead Infected can release spores regardless of stage.

To protect themselves from airborne spores, survivors wear gas masks. Those very rare who are immune do not need them, namely Laura Kinney.

The infection is unable to spread in open air areas, such as beaches, although some of these areas such as Rahleig and a suburban neighborhood in Pittsburgh have been shown with a high population of Infected. The infection mostly thrives in underground or enclosed areas commonly avoided by people, especially sewers, subway tunnels, and some buildings.

Source

 * http://thelastofus.wikia.com/wiki/Cordyceps_Brain_Infection