Pulmonary Nontuberculous Mycobacterial Disease, Ontario, Canada, 1998–2010

We measured the prevalence and temporal trends of pulmonary nontuberculous mycobacterial disease among residents of Ontario, Canada, during 1998-2010.Five-year prevalence increased from 29.3 cases/100,000 persons in 1998-2002 to 41.3/100,000 in 2006-2010 (p<0.0001).Improved laboratory methods did not explain this increase, suggesting a surge in disease prevalence. P ulmonary nontuberculous mycobacterial (pNTM) dis-ease is clinically challenging.Therapy entails complex antimycobacterial drug combinations, typically for 18 months (1), often with poor tolerability (2) and limited success (3).pNTM disease is increasingly common in Canada (4) and the United States (5-7), but its prevalence is not well understood.Determining the epidemiology of pNTM disease is difficult for several reasons.It is generally not reportable, so population-level data are not routinely compiled.The diagnosis requires clinical and radiologic information in addition to microbiological examination (>2 positive sputum cultures or 1 bronchoscopic or biopsy culture) (1).Finally, the chronic nature of pNTM disease dictates longitudinal study, illustrated by considering that only a minority with pNTM disease appear to be treated (18% in 1 study) (6), treatment succeeds in only 56% (3), and disease recurs in >30% of patients (2,8).These data indicate that most pNTM cases are expected to be chronic.Cases detected by isolation of nontuberculous Mycobacterium spp. in 1 year, generally remain prevalent over several subsequent years, regardless of the reliable appearance of subsequent isolates, with a disease duration that may depend primarily on patient survival.