(DeCandido's novelizations of Anderson's Films)
The global T-virus pandemic (tentative) was an outbreak of the T-virus, which successfully infested every inhabited continent, reducing the human population down to a million within five years. It was a direct consequence of the Raccoon City Incident of 2002.
The T-virus pandemic had its origins in Raccoon City, where two other outbreaks had run in succession, leading to the elimination of Umbrella's experts on the virus as well as the population of the city, respectively. During the evacuation of Raccoon City, Dr. Jim Knable, was unknowingly infected in the confusion. He soon after transformed into a zombie upon arriving in San Francisco, infecting others. The Mission District was quarantined early on, but the virus spread out further thanks to the airport. The President of the United States was forced to declare a state of emergency over the entire West Coast from California to Oregon and Washington. Aware of the Umbrella Corporation's responsibility, Drs. Hoyt and Love were called into the White House to explain the situation to the Joint Chiefs of Staff, where they identified themselves as the closest Umbrella had left to experts. During the meeting, news arrived of the virus appearing in Oklahoma, Michigan and Baltimore, Maryland. Immediately after the President's declaration that Umbrella and its employees had committed treason, one of his Generals transformed into a zombie and bit Dr. Love on the shoulder. Communication with the White House dropped soon after.
At the suggestion of his science division head, Dr. Sam Isaacs and Umbrella Chairman Albert Wesker began moving corporation assets to the various underground facilities maintained throughout the world. The corporation would soon become the only remaining entity with the ability to effectively defend itself against victims of its virus. It wasn't long before the rest of planet suffered the same fate as the United States.
A convention center in Baltimore, turned into a safe haven by Jill Valentine, is an example of a city haven for humans. It became a home to more than a hundred humans who managed to make a living among the ruins.