It is probably coming back because the strains are extremely virulent and you have too keep fighting them until they are completely gone or they will come back even stronger. I would take Inositol and N Acetyl Cysteine. They are both very good for the lungs. I would also make an extra strong batch of Colloidal Silver , much stronger than anything you can buy in the store. I would make it strong enough to be golden, like urine. Then I would gargle with it every few hours and swallow the residual. I would also take a homeopathic bronchial cough syrup. I like BT brand best. They have both a night time and a day time formula. Colloidal Silver is not going to make you worse. If you only take a few drops and what you need is an ounce, you might get worse because you aren't taking enough to do you any good. As expensive as it is, I can't afford to buy enough of it to cure myself of something like the flu. But I can make a gallon that is much stronger than what they sell at the store and get well.