Bite Chance is the likelyhood of a survivor being bitten by a zombie during combat in Zafehouse.

A survivor's base unmodified Bite Chance is 60%.

This is then modified by the weapon they are (or are not) carrying and whether they have the Grizzled Perk or not.

Below, for easy reference, are all the possible modified Bite Chance values a survivor may have in the game:

Unarmed 60%
Unarmed + Grizzled Perk 50%
Melee Weapon 50%
Melee Weapon + Grizzled Perk 40%
Ranged Weapon* 30%
Ranged Weapon* + Grizzled Perk 20%

*A survivor must be carrying sufficient Ammunition to fire in order to gain the bonus for a Ranged Weapon.