Have you tried running TDSSKiller
& what are the results?
On a clean PC, d/l Windows Defender Offline and run it. Be sure it's a clean PC you d/l & make it on, as a infected one will compromise the tool. Windows Defender Offline
Does your AV list it as just "svchost.exe" virus or does it give any more details as to the virus name/variant? If so, please post this information, it will help us to find a fix.