Humans cannot be turned into Wolf-Shifters by being bitten by a wolf-shifter (in wolf form, contrary to their werewolf predessessors). They can, however, trigger the wolf-shifter abilities in a human who already carries the wolf gene. They do this through draining the 'human" of their blood and feeding them their wolf blood. This is extremely dangerous, and rare, as the human can easily die of blood loss and the wolf gene could still be un-triggered after the attempt. Because of this, wolf shifters are rare.