Antivirus as of late seems to be less effective than years ago. I don't have any hard data to show that but recent experience. It used to be most of the time I could find some antivirus program to resolve an infection. But recently I've had many infections that could not be resolved by many antivirus programs). Three computers I own recently were separately infected. Two of them I tried many antivirus programs: Norton, McAfee , Webroot, ESET, BitDefender, MalwareBytes. MalwareBytes found many items during a scan and would clean some things up but the virus persisted. On two of the computers I gave up and had to re-install the entire OS. On another computer I finally tried Kaspersky and it did found many viruses and seems to have gotten rid of them. Given Wired's comments about Kaspersky I was a bit leery trying it, though it did a good job. Webroot Spysweeper used to be my favorite, but on these recent infections it would often find no sign of viruses at all, when there clearly were.
Antivirus software as has been reported seemingly to have given up being able to resolve all virus infections and have started to expand to providing other options to help, such as password manager's, backup and encryption to seemingly foil some viruses/spyware.
Below are some good antivirus software links to Amazon for more info.
Norton Security find on Amazon
Click here to find Kapersky Internet Security on Amazon