29M, 150lbs, 5’9”, Caucasian, smoker, otherwise healthy.

My husband suddenly became very ill around Halloween. He had a random fever spike to 101.5 that lasted for only a couple of days, then went away without any medicine use. He had 4 Covid tests (3 rapid, 1 PCR) and all came back negative and chest X-ray came back clear.

A doctor my mom works with suggested it may be fungal. How long would he have to get a blood test to determine this? He still has a cough but not as mucus-y and no fever, and is still sort of lethargic. If he went to the doctors this week or next, would they still be able to do a blood test to check for a fungal infection?

(Also, forgot to mention above he had been prescribed Codeine, Promethazine, Benzonatate, and Prednisone, all barely helped.)