Fall of the Argosi / Sebastien De Castell.

New to the ways of the Argosi, the tribe of wandering philosophers who seek to defeat evil by wit and guile, Ferius Parfax encounters a hideous plague, the Red Scream. Highly contagious, caught by the hearing of a deadly verse, it turns its victims into mindless monsters that destroy all human life they come into contact with. With the help of a deaf boy whom she has saved from two horrifying victims of the plague, she sets out to find the source of the Red Scream and overcome it's terrifying power. Along the way she is joined by another Argosi, Rosie, who purports to be so much wiser and more adept than Ferius, but who turns out to have her own dark secrets.

Adolescent.