I've been reading about viral vectors and am looking to incorporate it into my setting. From what I can see, it's possible to use viral vectors as a form of gene therapy, and retroviruses can work pretty well for these: https://www.genetherapynet.com/viral-vector/retroviruses.html
I don't understand the exact mechanics behind it, but essentially the retrovirus, with its genetic material being RNA molecules, would introduce its RNA molecules into the host's DNA.
There are some issues with this, from what I read: "the integrase enzyme can insert the genetic material of the virus into any arbitrary position in the genome of the host; it randomly inserts the genetic material into a chromosome. If genetic material happens to be inserted in the middle of one of the original genes of the host cell, this gene will be disrupted (insertional mutagenesis). If the gene happens to be one regulating cell division, uncontrolled cell division (i.e., cancer) can occur."
So - this can lead to cancer, specifically leukemia (occurred in some children in Europe IIRC).
Now, what I want to do is use this method to somehow make an airborne disease. Let's say that a genius biochemist is trying to treat his dying child and comes up with a form of retroviral gene therapy, but it goes wrong and wreaks havoc. The virus turns into a deadly, contagious airborne disease.
How could this potentially occur?