Changing epidemiology of nontuberculous mycobacterial lung disease over the last two decades in a region of the Basque country

Recent studies suggest an increasing prevalence of nontuberculous mycobacteria (NTM) lung disease. The aim of the present study was to describe incidence rates of NTM lung disease and trends therein in our area over a 20-year period. This was a retrospective study of all cases of NTM lung disease between 1997 and 2016 that met the 2007 American Thoracic Society criteria. We analysed the annual incidence rates, species of mycobacteria isolated, trends over time and annual mortality in 327 patients. Mycobacterium kansasii was the most common mycobacterium isolated (84%), followed by Mycobacterium avium complex (MAC) (13%). We compared two periods: 1997–2006 (257 cases, 79%) and 2007–2016 (70 cases, 21%). The incidence rates tended to decrease across these years, with a peak of incidence in 2000 with 10.6 cases per 100 000. There was a clearly decreasing trend in M. kansasii infection, not only in the first period (incident rate ratio (IRR) 0.915, 95% CI 0.88–0.90; p<0.0001) but also in the second (IRR 0.869, 95% CI 0.780–1.014; p=0.080), reaching 1.8 per 100 000 in 2016. In contrast, MAC infection tended to increase across the two periods (IRR 1.251, 95% CI 1.081–1.447; p=0.003). In our region, the incidence of NTM lung disease has notably decreased in recent years. M. kansasii had high incidence rates in the first decade but clearly decreased in the second decade.