OutbreakEditAlice Harris, a Carrier of the Rage Virus, was taken to District One and put in isolation. She was visited without authorisation by Donald Harris, who kissed her. However, Don was infected with Rage by Alice's saliva from the kiss, and after killing Alice, the infected Don escaped the isolation cell and began spreading the Infection. (28 Weeks Later)
District One was thus put into Code Red lockdown, and civilians were herded into safe rooms with locked doors. However, the Infected broke into the safe rooms and began infecting and killing the trapped crowds. Hordes of Infected and surviving citizens began to escape from the enclosures into the streets of District One. Snipers were first ordered to shoot only Infected, but as the numbers of Infected grew and overwhelmed the surviving populance and it became more difficult to tell Infected from uninfected, snipers were ordered to kill everyone at ground level, infected or not.
District One was soon after firebombed, but not before both civilians and a large number of Infected escaped into London. Following the escape of Infected into London, the US Army began venting poisonous gas and sending soldiers armed with flamethrowers into the city to exterminate the Infected. (28 Weeks Later, 28 Days Later (comic series))
In the final scene of "28 Weeks Later" the helicopter which transported Andy Harris who was carrying the Rage Virus but somehow didn't develop the symptoms and his sister Tammy Harris out of England can be seen crashed while a french radio transmission calling for help can be heard in the background. Infected are seen running towards the Eiffeltower meaning that all the efforts of the Military containing the Virus have failed and that the Virus has now reached the European mainland.