Yes they have! Adeno-associated viruses (AAV) have been used to deliver gene therapies, with one prominent example being Zolgensma, a treatment for a rare genetic disease called spinal muscular atrophy.
Thanks. Interesting. Seems that the term I want is "viral vector".
Clearly some bugs still to work out (bad pun, sorry) but seems like a very promising approach though I think eventually the fix should be something that is also present in off-spring (which currently is probably illegal so and will change the risk assessment needed)
If so what is the name for that technology and what would be the right search terms to find the literature?
From bacteria we got CRISPR.