5

I would also try VirusTotal as it has 32 different engines and if there are loads od scanners detect it you didn’t mention anything about that.

A copy and paste or image of the VT/Jotti detections would be nice ?

You also didn’t tell us what the malware name or the infected file name and full location was this helps us with any advice we give e.g. (malware name, C:\windows\system32\infected-file-name.xxx) ?
Check the avast! Log Viewer (right click the avast icon), Warning section, this contains information on all avast detections.

We can’t realistically give advice on what to do as I don’t think we have enough information.