Immunity to Disease
Wererats have a reputation for surviving against impossible odds. All of them share a highly developed immunity to disease; they can even carry and transmit deadly infections without suffering their effects. This benefit is the result of the Birthing Plague, the infection that continually courses through a wererat's blood. If anyone managed to cure a Ratkin of its diseases, the beastie would lose its spiritual essence, reverting to a human or a normal rat. Metis wererats afflicted with such a punishment die.