Influence of Climate Variables on the Rising Incidence of Nontuberculous Mycobacterial (NTM) Infections in Queensland, Australia 2001-2016

Abstract

Reports from different countries indicate a rising incidence of NTM pulmonary disease. Many infectious diseases have seasonal variation in incidence and major weather events and climate change have been implicated in disease emergence and outbreaks. The aim of this study was to describe the incidence of NTM infection in Queensland, Australia over a 16 year period and to explore the relationship between climate variables and NTM notifications.Methods: NTM data were obtained from the Queensland notifiable conditions database for the period 2001-2016. Data on average rainfall and temperature were obtained from the Australian Bureau of Meteorology. Poisson regressions models were built to model the notification rates per 100,000 population over time and to estimate the incidence rate ratios (IRR) by sex, age, and Hospital and Health service (HHS) district. Analyses were conducted for total NTM notifications, individual NTM species, and for all slow-(SGM) and all rapid-growing NTM (RGM) species for differences in notification rates by sex, age, and HHS over time. Cross correlation coefficients were used to examine the relationship between rainfall and temperature data and NTM incidence over time in each HHS. Results: 12,219 cases of NTM were reported. The most common species were M. intracellulare, followed by M. avium, M abscessus, M. fortuitum, M. chelonae, and M. kansasii. The estimated incidence rate increased from 11.10 (2001) to 25.88 per 100,000 (2016). The estimated IRR increased for all common NTM species, except M. kansasii which remained stable. Each NTM species showed a similar pattern in patients’ sex and age; the highest IRR was observed among patients aged 50-79 years. Although increased IRRs were observed for most NTM species, geospatial heterogeneity was observed. Overall NTM incidence increased 9 months after the rainy season in the north; SGM notifications increased 8-10 months after rainfall increased, however 6 months after increased rainfall, RGM notifications decreased. Three months after an increase in rainfall, NTM incidence decreased in the west (predominantly M. avium). Variation in temperature was not found to be associated with overall NTM incidence; however, M. abscessus incidence decreased 6 months after an increase in temperature in the north. M. intracellulare incidence was not associated with rainfall or temperature in any region. Conclusions: The incidence of NTM infections increased from 2001-2016. Variations in rainfall may play a role in environmental exposure to some species of NTM. Spatial variation in IRR suggest that there may also be other environmental drivers of transmission. Show more