Check the original link the data up.submitted for peer review states a 90% accuracy rate. It also is stated directly in the quoted text post by Roman here. Given my experience with K9 units 90% or above is easily believable drug dogs are near 100% accurate they rarely miss even the smallest amount. I have seen a dog find a single seed and the ash from marijuana cigarette behind closed doors from 30+ feet away. I have seen a dog find residue from 40 mike mike MK19 ammo four months after they were carried in the bag and only the unfired munitions were carried in it not the spent cases so the only material was by surface contact of new munitions that K9 smelled that from passing by in an airport line walk through truly impressive levels of sensitivity.
I would expect a K9 properly trained to key in on sweat , mucous and tears from a COVID person with laser like precision.
Thanks for the info and perspective.