One Test, Two Opinions

Yesterday I took Brian into see the physician because he has been sleeping 12-15 hours a day. His regular physician had no openings, so we saw the doctor who was on call. They took blood and ran tests for wide variety of possibilities.

I just got a call from the nurse relaying the information from both physicians.

Physician 1: Everything looks normal including his white blood cell count, although his blood work indicates that he might have had a "little virus." If he continues to sleep like this we should bring him back and they will re-test for mono.

Physician 2: Everything is normal and we just don't know why he has been so tired. Come in and we will give you this machine to take home. He will sleep with a sensor on his finger that will measure how much oxygen he is getting which will tell us if he has any kind of sleep apnea, which can cause fatigue.

Huh. Does anyone know what would indicate "a little virus"? Is that code for, "That is the most likely explanation given that our tests came back negative" or does it mean that there was some piece of information that one physician noted and the other did not?