Briefly, 560 μL lysis buffer was pipetted into the microcentrifuge tube, and added with 140 μL cell culture media, mixed by pulse vortexing, and incubated at room temperature for 10 min. Later, 560 µL ethanol (96-100%) was added and mixed by pulse vortexing for 15 sec. After that, 630 µL of above solution was applied to the QIAamp mini column, centrifuged at 1000 g for 1 min. QIAamp mini column was placed to another collection tube, and the tube containing the filtrate was discarded. Then, the column washed twice with washing buffer and the bound RNA in the column was eluted with 60 μL of elution buffer. The viral RNA was analyzed using RT PCR. Complementary DNA of the viral RNA was synthesized by cDNA synthesis Kit (Fermentas,Vilnius, Lithuania). Briefly, the 20 µL of mix reagent containing SRV primer set consisting of an upstream primer ‘5-CACCTCTYTRCTYAYAGAGCTGA-3’ and a downstream primer 5’-GAAACTGCGCCTGTCT-3’ and dNTPs was mixed with 5 μL of RNA sample. PCR amplification was performed by following protocol