@taya Hello Taya. To answer your question, mac is short for mycobacterium avium complex. It is a nasty infection that people with bronchiectasis sometimes get. This group is mainly comprised of people that have it or have had it. I hope you will read over the many posts that have been written here and on the Discussion board. You will find lots of info on our pages. Keep in mind that not all people with bronchiectasis get mac, though most will at some point in their life. It would be a good idea for you to learn all that you can about it so that you can try to avoid picking it up or learn how to identify it should it ever come up. I wish I had known that hot tubs were so dangerous for patients with bronchiectasis. I feel certain that is how I caught MAC. How are you doing now with your bronchiectasis?