Incidence trends of nontuberculous mycobacterial pulmonary infections in Australia, Cambodia, Japan, Thailand, and the United States

BACKGROUND: Nontuberculous mycobacteria (NTM) are environmental organisms increasingly causing chronic respiratory infection. Although NTM pulmonary infection is rising globally, most studies are single-country. This study evaluated temporal trends in pulmonary NTM incidence across Queensland (Australia), Phnom Penh (Cambodia), Japan, Thailand, and the United States (US), and described regional species distribution. METHODS: Laboratory and insurance claims data were used. Incident infections were defined using region-specific criteria. For Queensland, Japan, and Thailand, data and denominators covered entire regions. US estimates included Medicare beneficiaries aged [&ge;]65 years, and Cambodian incidence was estimated from Phnom Penh data and standardised nationally. Incidence rates per 100,000 population and incidence rate ratios (IRRs) were calculated overall and by sex. Age-stratified analyses and species distributions were summarised where data were available. RESULTS: Pulmonary NTM incidence increased in all regions and was highest in Japan (47.20-57.40 per 100,000) and lowest in Phnom Penh (0.23-0.38). Queensland showed the largest increase over 24 years (IRR 7.06, p<0.0001). Female predominance occurred in high-income regions, whereas Thailand showed ~1.5-fold male predominance and Phnom Penh showed no sex predominance. Incidence was higher among individuals aged [&ge;]60 years. Mycobacterium avium complex predominated in Japan and Queensland, and M. abscessus in Thailand and Phnom Penh. CONCLUSIONS: Pulmonary NTM incidence increased in all regions, varying by demographic patterns and species distribution. Differences largely reflect under-ascertainment related to diagnostic capacity and tuberculosis-focused health systems rather than true infection burden. Strengthened surveillance and diagnostic capacity are needed to define the global burden of NTM pulmonary infection.