Viral RNA is relatively stable than mRNA from cells? - (Nov/25/2010 )

Recently, I did some experiments-isolated viral RNA in sera for RT-qPCR. I found that the protocol is easy and the requirement for controling RNase degradation is less strict than that of mRNA. I wonder that whether the Viral RNA is realtively stabler than mRNA in structure? According to some reference, viral RNA can binds to the proteolipids in sera. May be this can protect them form degradation. But when the lysate buffer was added, the viral RNA was isolated form this "coat", whether their complicated secondary structure could help them from the degradation of RNase? Many thanks in advance!

Anyone konws? Give me some ideas. Many thanks