There are several distinct songs titled "Infected" that have received the Nightcore treatment. Knowing which one you want is the first step:
The "Nightcore" standard is typically a 20-30% increase in both speed and pitch.
A cinematic rock version with a heavier, more melodic sound. It is often found as a Sped Up / Nightcore edit for those who prefer rock over electronic music.
If you want to "infect" a song yourself, here is the standard procedural approach used by many creators: