: Lana is infected; staying close to or holding Amy's hand (R1 button) reverses her contamination and can even heal her.
Below is a helpful summary of its core gameplay and common tips for those attempting to play it. Amy PSN
: You can intentionally let Lana's infection progress to a "zombie-like" state to sneak past certain enemies, though this is a "double-edged sword". Helpful Tips for Players AMY Review for PlayStation 3 - GameFAQs : Lana is infected; staying close to or