Win32 Downloader PKU [TRG] Virus or Malware

I use the free version of Avast in addition to Malwarebytes that I use on my Inspiron 14R - Windows 7.  This afternoon Avast started with pop-up warnings saying:

Trojan Horse Blocked. 

Infection:  Win 32 Downloader PKU [Trg] and 

Infection:  Win 32 Malware - gen

Action:  Moved to chest.

I ran Spybot and Malwarebytes.  They found and cleaned up some stuff but the pop ups keep coming. 

These warnings are popping up every 5 minutes or so.  I Googled  "Win 32 Downloader PKU [Trg] " and the only reliable site talking about the malware is a an Avast forum which recommends posting a long report, disabling Avast, downloading and running other software programs and so on.  The forum posts on the issue are very recent but what they are suggesting seems a a bit too complicated for me. 

Is this a serious issue and is there a an easier way to deal with  it.  I don't understand why it's only an Avast issue.  Can I do a restore or should I buy or use  some other anti virus software?  

Any advice would be appreciated.