Syag, I am not playing a doctor. To clarify – if he thinks he need to go to the doctor, he should. I am suggesting additional precautions only. I am considering here that he presumes it is a flu and it could be Covid. Same goes for people presuming they have sudden allergies. Everyone with possible covid symptoms should slow down and find something to do for a couple of days.
Rough estimate: flu is defintely back this year after missing last year. there are 800 flu hospitalizations per week and 50,000 with covid, so if someone is having a difficult case, R’L, covid seems more likely. Probably less for a young person, though.