Although we seem to think we have a pretty strong hold over the viruses ability to plague us, it is still true that some of human kinds deadliest diseases are still virally bound. Not to say, by any means, that we havn't achieved a lot in the field, however, we still lack control over all viral infections, indicating non completion of a mastery of the field itself.
Some of the viruses we've managed to almost completely wipe off the face of the earth, thanks to the help of immune system boosting from vaccines, include: smallpox, polio, measles, mumps and rubella. Vaccines for these viruses have assisted in building immune system antibodies against these particular infections, almost eradicating their inflicting presence within humanity.
Another major player in the game of modern virology is antiviral drugs. These drugs, although rarely responsible for curing a viral infection completely, will often keep the virus from spreading, lessen the noticeable effects of its infectious presence and / or prevent the effects of the viral infection from being noticed.
Although we've done much in this day and age to alleviate suffering from viruses, it would be most prudent to note that some of the largest causes of medical suffering in our world day are virally based. AIDS itself is a viral disease, and even many forms of cancer are thought to be cause by viral infections.