The rogues are being updated/morphed all the time. Almost all AV's, by nature of their reactionary process, will only detect the latest variant when they have a sample of same, and add it to the database. By which time a new variant is released.
This is multi million dollar business. The only way to prevent such things is to use a good behaviour blocker, and/or have a multi-layered security approach that you understand and can manage.
As you see, just an antivirus is sometimes not enough.
With your specific recent infection, I'd be inclined to download the free version of MBAM (get it here)
Malwarebytes install it, update it, and run a quick scan. Remove anything it finds.
Mbam is a very good demand anti malware scanner. Like Spybot or AdAware, but updated.