failed to preform actions on viruses found in previous scans

Avast Mac Security
1

avast! antivirus Mac Edition 3.11R0 (ServiceKit 1.41)
Greetings
Foolishly I thought that when avast identified a virus that it automatically took care of it.
Now I know that the user has to choose how a virus is dealt with.
My problem is that viruses have been found but I have not deleted them.
My recent scan does not show the earlier viruses avast found.

How can I start a scan that will find the the viruses it found before?

What should I do with a decompression bomb?

Your help would be appreciated, Thank you

2

Do you know what threats where found in the earlier scans?

A Decompression bomb is an archive with a unusually high compression ratio, do you recognize the file name? Can you post which files were detected?