The ability to spread viruses and diseases through bites.
The user's teeth and/or saliva contain infectious diseases and viruses which they can spread to others with a bite.
- Some targets may be immune.
Traditional werewolves (various) can spread the werewolf condition to other beings with their bite.
... As well as different vampires (various) can transmit the vampire condition other beings with his bite.
Yuki Nagato (Haruhi Suzumiya) infecting Mikuru with nanomachines with a bite.
After being injected with a refined Lizard serum, the Lizard (Ultimate Spider-Man) could infect others with his bite...
...with the resulting Lizard Virus transforming those bitten into Lizards.