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 ≥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 ≥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.

KEY MESSAGES

• Pulmonary NTM incidence increased across all five study regions, however varied substantially by region, age, sex, and species.

• This study provides the first NTM incidence estimates from Thailand and Cambodia, where limited diagnostic capacity and tuberculosis-focused health systems influence observed incidence.

• Combining laboratory and claims data across high- and middle-income regions provides robust, comparable estimates to inform NTM surveillance and public health planning.