When attacking with this weapon a natural roll of 6 when rolling to hit means that the target has been infected with the disease.
The diseased model must take a Toughness test. Roll a D6, if the result is higher than the Toughness of the model taking the test he will suffer an automatic wound in addition to any wound(s) the dagger may otherwise inflict.
Models of undead and possessed are immune to this disease and do not take the test.