Please enable the Risk tracer in SEPM server console to see the system virus detection log.
Following information to allow the risk tracer in SEPM server console.
1. Open the SEPM server console.
2. Go to policy and slect Antivirus and Antispywer policy.
3. Duble click and open the Antivirus and Antispyware policy.
4. Click on File System Auto-Protect and go to Advanced.
5. Click on Risk Tracer and Mark to Enable the risk tracer.
you can also define the maximum lenth of risk logs..
your system risk log problem will be resolve