[2] As an example of environmental specimens, the viral load of norovirus can be determined from run-off water on garden produce.
HIV positive patients on long-term combination antiretroviral therapy may present with an undetectable viral load on most clinical assays since the concentration of virus particles is below the limit of detection (LOD).
[citation needed] There are many different molecular based test methods for quantifying the viral load using NATs.
Extraction of RNA from plasma requires specialized equipment, reagents and training, which might out of reach for medium to small laboratories.
EDTA blood can be stored at room temperature for 30 hours, and separated plasma for extended periods of time at -70 °C without significant decreases in viral load.