A "modified virus" refers to a virus that has been changed or altered in some way, usually in a laboratory, to have certain desired characteristics or properties. Full definition
He is renowned for his use of genetically modified viruses to combat malignant disease. (cityofhope.org)
Instead, they plan to see if they can genetically modify the virus to be safer, but still work as a possible treatment for brain cancer. (newscientist.com)
Trying to mimic randomly occurring mutations that lie at the heart of all tumors, the Salk researchers used modified viruses to shuttle cancer - causing oncogenes into a handful of cells in adult mice. (salk.edu)