Answer: 28 Days Later
In this movie, Jim (Cillian Murphy) wakes up alone in an empty hospital 28 days after getting into an accident, during his job as a bicycle courier, and finds London empty. When he begins to find survivors, they band together in order to find a safe place, but soon, they begin joining the destructive infected humans when they too get infected by their blood. When they come across the army, they think they're safe, but things get much worse when they encounter uninfected monsters. "28 Days Later" put zombie thrillers back on the map in 2002, and it was a great, creepy film.