It's safe to assume ALL rats have myco, except those in highly controlled labs.

Your rat has an URI, and will need to stay on meds to help get the infection back under control.

Myco is usually kept in check by a rats immune system. When that immune system is compromised by another illness, myco will flare up as well.

If your rat gets over this sickness, I wouldnt continue to treat for myco. Good chances are it will never be completely cured.