[VOIPSEC] RTP-borne virus examples?

[John Todd]

Has anyone seen any "wild" virii transmitted via RTP?  I have heard 
of the theoretical transmission of such viruses and heard rumors 
about them, but as have yet to see one for myself.  I would be 
interested in any references or documentation of such items, and what 
(if anything) is being done on any edge devices to counter the threat.

Apologies if I'm far behind the times on this type of thing and there 
is an obvious list that Google simply did not show; I don't often 
keep track of client-side virus issues.

JT