(Covers information from Anderson's universe)
The outbreak of the t-Virus in Raccoon City as portrayed in Resident Evil: Apocalypse began within hours of the reopening of the Hive, and lasted only days before the city's destruction via the detonation of a nuclear missile.
The outbreak occurred shortly after the Infection of the Hive after an unnamed doctor ordered the Hive be reopened. The group present for this operation was not prepared for what they found; several members were armed, but the team was ultimately completely defenseless against the large number of the undead and B.O.W., which proceeded to escape the facility and overrun them. The infected soon moved to the surface and then out into the city. Almost immediately, they began to attack the local population, spreading the infection at a monumental rate, with it becoming airborne in a matter of hours.
To everyone else, it appeared to be a senseless mass murder spree with people becoming "recruited" quite easily. The police attempted to arrest the infected, getting bit themselves. Jill Valentine was suspended from the RCPD for shooting the infected, even though she knew it was the best option.
As the outbreak progressed, the Umbrella Corporation began evacuating priority employees and other assets by armed escort, followed by civilians at a series of checkpoints to ensure that contamination be contained, sealing each checkpoint whenever the virus reached it. Unfortunately, however, the virus quickly reached the final checkpoint after a man had a heart attack and became infected, biting Sergeant Peyton Wells. This unexpected event forced Major Timothy Cain to close the gates to prevent the infection from possibly spreading outside the city. He then proceeded to have his soldiers use gunfire to force the remaining crowd away from the city's border, sealing the last checkpoint and exit from the city for good.
With the final avenue of escape now gone, the fate of the Raccoon City's remaining residents was sealed. Those who were not killed by the undead horde and reanimated to become a part of it were ultimately murdered by Umbrella's attempts to hide their mistake.
When Umbrella accepted that they could not simultaneously contain the infection and salvage Raccoon City, they sought to gain what they could from the debacle by testing their "Nemesis Program" on the city's streets before its destruction. To ensure the programs battle efficiency they pitted it against a team of S.T.A.R.S. operatives, which it dispatched with ease. Once that was accomplished Nemesis was directed to battle Alice, though the creature which was revealed to formerly be Matt Addison was eventually defeated by her and subsequently killed in a helicopter crash.
As dawn broke three days after the infection began, the U.S. government, presumably working alongside Umbrella, made a desperate last move to "contain" the outbreak for good by dispatching a nuclear warhead that exploded over Raccoon City Hall. The bomb was successful, leveling the city to the ground, destroying the undead and presumably erasing all other evidence of Umbrella's deeds in the process. Soon after, the blast would be passed off by Umbrella as an unfortunate accident at the Raccoon Nuclear Powerplant.
Though the city was destroyed, Umbrella failed to eliminate all witnesses who could expose the truth. Alice, L.J., Angela Ashford, Jill Valentine, Carlos Olivera and the unnamed helicopter pilot escaped the nuclear blast, and subsequently sought to expose what Umbrella had done. They were initially successful, but Umbrella managed to discredit the evidence against them as an elaborate hoax and have the group labelled as fugitives, once again ensuring that the corporation would survive.
This victory was short lived, however, as despite their precautions, Umbrella suffered another containment failure, this time in Tokyo. With this catastrophic mistake, the infection spread around the world. This would eventually lead to the Global T-Virus pandemic, bringing humanity to the edge of extinction and destroying the majority of lifeforms on Earth. Following the outbreak, Umbrella moved their operations to various underground facilities around the world.
Ten years after the start of the pandemic, Alice would return to the ruins of Raccoon City and the Hive in order to find an anti-virus capable of killing everything infected with the T-virus. With help from a group of survivors, she succeeded in doing so, which began to end the global pandemic for good, although it would take years for the anti-virus to fully circle the Earth.