I'm not sure. I recall there being a lot of criticism about how they were testing for presence of covid, basically setting the sensitivity to the point where it would register normal levels of viral fragments as an infection.

I am no expect but I would guess it would need to be reproducing to be at a level that is detectable.

How many virus cells could a couple midge bites actual put into the blood stream.

Wumbo

Virus detection doesn't even imply the virus was successfully reproducing in the patient. It could have just been floating around in his system from exposure.