Hi,

You can use molecular methods such as Reverse-transcriptase polymerase chain reaction (RT-PCR) and real-time RT-PCR. You can also use Plaque assay/Immuno-Plaque assay/ immuno-fluorescence techniques for quantification of Dengue viruses. Alternatively Flow Cytometry-Based assays are available for titrating Dengue Viruses.

I use Immuno-plaque assay for quantification of Dengue viruses but it is for vaccine samples.

Good Luck.

yes you can do by Plaque assay if it is showing CPE in BHK 21 cells. You seed definite number of cells and infect with different dilution of the prepared stock virus. After 2 hrs of adsorption, give a PBS wash and add 1 ml of 1% CMC+ DMEM+1% FBS+ Antibiotic mix. Keep it for 5 days in CO2 incubator without disturbance. Fix the cells by adding 1ml 30% formalin on top of the overlay for 4 hrs at 37 degrees and then remove the whole overlay from the wells. Add 400ul of Crystal violet to the wells and keep them for staining followed by a gentle wash with tap water. And you can see the plaques and quantify them by,

 (no. of plaques x the dilution factor x 1000) / volume of virus added for infection = pfu/ml of virus.