For me it is slightly lower oxygen , by 1-2% for the first day, second,3 day low fever 99-100 and more cough, some more sputum not necessarily color changed, and intensified cough. And there is this strange thing- I can smell ozone in the air. It happened twice already so I think it’s the sign of the flare. I wait two days to see how it develops, then email my pulmonologist. If the office responds, I have a chest X-ray and once I took my sputum sample for respiratory culture to the lab. Then I would start an antibiotic. The last time the office did not respond quickly, I went to the hospital immediate care, was tested for Covid, flue and multiple respiratory viruses. One came back positive so based on this I was given prednisone no antibiotics. Well I still cough a looot but it’s only second day of the steroid. Oh at the IC clinic they checked my lungs, were clear. I will go there again in 2-3 days to check lungs. I am sorry it’s so long but I still cannot figure out the real definition of a flare and when to seek the medical attention