My suggestions is simple Deletion isn't really a good first option (you have none left), 'first do no harm' don't delete, send virus to the chest and investigate. After a period of grace you can be relatively sure that the file in the chest is a good detection.
Files with just a little tagged onto them when detected they may be able to be repaired. Only those where it may be possible will have the Repair option active (otherwise it will be greyed out). The repair works in conjunction with the VRDB function in avast, you should runs this shortly after installing and choosing how you want it to update (default duration 21 days). Referr to the avast help file, Healing.
The VRDB only protects certain files, .exe, dll and other system files, it doesn't protect data files or all files, it is not a back-up program, so there are going to be many occasions where repair won't be an option.
Only true virus infection can be repaired, e.g. when a virus infects a file it adds a small part to it, provided that file is one that avast's VRDB would monitor and you have run the VRDB, then it may be possible to repair the file to its uninfected state.
However, for the most part so called viruses, trojans (adware/spyware/malware, etc.) can't be repaired because the complete content of the file is malicious.