Broadly defined, transfection is the process of artificially introducing nucleic acids (DNA or RNA) into cells, utilizing means other than viral infection.
https://en.wikipedia.org/wiki/Transfection
The theory is that you can "create" an "infectious clone" in the lab and then spread it to humans.
I call it "poisoning". And it falls well within the category of movie "special effects".
Are the actors ("patients") who represent as "transfected" really sick?
Depends on how convincing you want to make the "special effects".