As Shaun walks to the corner store in one of the awesome one-shot scenes, he passes a road sweeper. The radio on board the vehicle tells of how a space probe called Omega 6 started the virus. Apparently it entered the atmosphere several days early over southwest England, breaking apart over dense population centres. This explanation is an echo of Romeros most famous film, Night of the Living Dead, when a space probe breaking up in the atmosphere is blamed for the cause of the dead returning to life and attempting to consume the living.