The Fall
The Fall (also sometimes referred to as Zero Hour) was a major event within the Dying Light universe, with the game, Dying Light 2 Stay Human taking place 15 years after the incident.
Overview
The Fall describes the later years(2024-2026) following the release of a variant of the Harran Virus, known as THV, from a Level 4 GRE lab in Geneva, Switzerland, the subsequent death of 98% of the global human population and the resulting collapse of civilization. It isn't clear when it exactly started, though it could be said to begin with the release of the variant in around 2020/2021 and concluded in early 2026 when the last functioning city on Earth, Villedor, home to over two million people, was devastated by the Black Monday bombings, wiping out the majority of its population, destroying vast swathes of the city and plunging the city into complete chaos. The Fall progresses to the point where only 20 cities are deemed safe though, at some point, all of these cities, except for Villedor, are destroyed by missile strikes to stop the infection. Villedor was scheduled to be hit by missiles in February 2025, though it is unclear if the other 19 cities were to be destroyed at the same time or not.
It is unknown if any official government or organization existed past this point, other than the factions present in Villedor. However, Waltz remarks in his recordings, made in 2036, that he has lost funding, hinting at a potential authority of some kind that is still operational at this point.
Cause
The Fall was not a direct consequence of the events of the first Dying Light game set in Harran, as a vaccine was eventually discovered that neutralized the threat of the virus contained within the city, ushering in a brief period of safety.
The variant, apparently unaffected by the vaccine, differed slightly from the originally Harran virus and was supposedly developed by the GRE as part of an investigation into the potential military applications of the virus. This research was conducted in secret despite the GRE's promise to cease all THV laboratory operations. How the disease escaped the lab is unknown as of right now.
Post-Fall Earth
From the evidence we have and the game's introduction, the entire planet is a lonely and dangerous place where no human is safe. Apart from Villedor, the only inhabited settlements are "small enclaves" separated by great distances. Hakon remarks that it is easier to life by the sea, and some characters make references to settlements such as "New Paris". Aiden says he is from a place called "Crossdale River", over 2,000 km (via indirect routes) from Villedor, though it is unclear whether this is a settlement or simply a geographic point of reference. Aiden remarks that, to his knowledge, the island of Great Britain has approximately four settlements left and that London is likely no longer in existence.