It's one of the big advances of our time. (And perhaps ironically, the most useful virus may turn out to be HIV).
But another virus is now showing promise. Remember polio? Thank vaccination for the fact that most of us can't. (And thank anti-vaxxers if any of us see it again, but that's a side issue).
Scientists have redesigned polio to make a virus called PVS-RIPO. This virus likes...cancer cells. And only cancer cells. It's erased or significantly reduced brain tumors...and not just in monkeys, either.
It's very likely that the "cure" for cancer will turn out to be an entire pack of redesigned viruses. And that the descendents of the virus that crippled Franklin D. Roosevelt will save a lot of lives.