The study did not look at whether family members or other close acquaintances ended up containing measurable numbers of copies of the virus. The patients were tested and the study verified that the (altered) genetic data from the virus was excreted normally.

The virus was deliberately defective and unable to replicate, so the copies made for use in treatment are the only copies that would ever exist. This also ensures that dose control is effective, if the virus could replicate then further copies of the gene would be inserted.

Is there any concern that viruses could mutate and once again start to replicate?

Thanks for the tldr; I hadn't realized that was possible.