There are just so many Anti Virus progs. out there, some being free!
They all have diffrent detection rates, so I try a new 'free' prog. from time to time.
You might like to try : A.squared - It's a stand alone prog, so can be used in conjunction with other progs, the
same as you can with Malware Bytes Anti malware.
I've just changed from AVG free to Avira Anti Vir free, and this picked up on viruses that AVG did not find!
If I have an inkling of infection, I'll try the online scanners as well, for example: Windows live online scanner
just to mention one, there are so may if you google for them!