Someone’s just asked me if it’d be possible to design a virus specifically to kill people with a certain given genetic signature.  I have a feeling that the South African security services tried to cook up an ethnically specific biological agent in the ’80s, but am not sure whether this is an urban myth.  Any suggestions?

Similarly, would it be possible to engineer a virus to deliver some kind of gene therapy for this or that condition, and then release it into the wild?  (I’ll ignore the moral problems of treatment without consent – I’m just interested in the possibility at the moment.)  Has there been anything published on this theme?*

*I’m sure there has.  What I actually meant was, “Could someone give me a reference or two?”.