Could you explain what risks there are in trying to isolate attenuated viruses from the human population? What are the ethical issues? Not the use of such an at

Could you explain what risks there are in trying to isolate attenuated viruses from the human population? What are the ethical issues? Not the use of such an attenuated strain, just the isolation. Just a small correction on the 69 deletion strains - they are all in gene coding reasons, but they are both frameshift and non-frameshift mutants.