This is a prospective observational study using whole genome sequencing (WGS) to investigate whether new strains (other than the initially identified strain(s)) of M. avium are responsible for persistently culture positive sputum during treatment (refractory disease), or the reversion to culture positive sputum after prior conversion to negative. The study will further investigate for differences between participants living in the Toronto/York region versus participants living elsewhere. The primary goal of this prospective observational study is to understand why some patients with M. avium lung disease have persistent or recurrent M. avium in their sputum despite treatment. The aim is to understand whether it is usually due to treatment failure or new infection.