Avast Mac Security found some viruses, but not all

I’m using Avast Mac Security 12.5, virus definition version 17031000, which I installed yesterday, due to a virus infection.

This is on OS X El Capitan, 10.11.6.

My previous anti-virus, Avira, was worthless – starting getting uncontrollable popups while in the Safari browser.
Running a system scan with Avast, which took over 5 hours, it found 86 viruses, which I deleted; but today am still getting the same behavior in Safari. Having better success running Chrome.

I am rerunning a system scan but so far no infections found. I notice that Avast says ‘Unable to scan: 619’ Why can it not scan that many files?

And is there any way to update the virus definition? Would like to get rid of whatever is on my Mac…

thanks,
Rick Casey

Your VPS is already up-to-date.

https://blog.avast.com/2014/02/28/how-do-i-handle-files-that-avast-cant-scan/

Why can it not scan that many files?
The message should tell you why