Lyssa X (noun): Lyssa X (also called "Lyssavirus X" or "Rabies X") refers to a mutation of Rabies with a much shorter incubation period of several days, as opposed to several weeks. Rabies, one of many similar viruses in the Lyssavirus Genus, is characterized by causing those infected to become highly aggressive, irrational, and unresponsive to attempts at communication. Other than its rapid onset, Lyssa X is otherwise identical to Rabies. Rabies is kept from rapidly spreading because it can take anywhere from 3 weeks to 2 years to affect it's host, but Lyssa X has overcome this limitation. The term Lyssa X was originally coined by OZORT, and is considered a fictional virus. It is also considered a zombie virus by zombie survivalist groups, as this mutation could very easily lead to a widespread zombie outbreak.

"Lyssa": Greek, Frenzy
If Rabies ever mutates into Lyssa X, we're all fucked.
by Edward Stevens August 25, 2006