Dust events affect the occurrence of influenza: A case-crossover study in an arid city of China

Background: Air aerosol is believed to be an important pathway for infectious disease transmission like COVID-19 as well as influenza. Therefore, we hypothesized that there might be a strong association between dust events and influenza, especially in semi-arid areas. This study aims to explore the effects of ambient particulate matter (PM) and dust events on laboratory-confirmed influenza cases in a semi-arid city. Methods A descriptive analysis of daily laboratory-confirmed influenza (influenza) cases, PM (PM 10 and PM 2.5 ), meteorological parameters and dust events were conducted from 2014 to 2019 in Lanzhou, China. The Case-crossover design combined with conditional Poisson regression models was used to estimate the lagging effects of PM and dust events on influenza. In addition, a hierarchical model was used to quantitatively evaluate the interactive effect of PM with ambient temperature and absolute humidity on influenza. Results We found that PM and dust events had a significant effect on influenza. The effects of PM 10 and PM 2.5 on influenza became stronger as the cumulative lag days increased, the greatest estimated relative risks (RRs) were 1.018 (1.011,1.024) and 1.06 1(1.034,1.087), respectively. Compared with the non-dust days, the effects of dust events with duration ≥ 1 day and with duration ≥ 2 days on influenza were the strongest at lag0 day, with the estimated RRs of 1.245 (95% CI: 1.061–1.463) and 1.483 (95% CI: 1.232–1.784), respectively. Subgroup analysis showed that pre-school children and school-aged children were more sensitive to PM and dust events exposure. Besides, we also found the low humidity and temperature had an interaction with PM, which could aggravate the risk of influenza. Conclusions Ambient PM and dust events exposure may increase the risk of laboratory-confirmed influenza, and the risk of laboratory-confirmed influenza increased with the dust events duration. These findings will provide additional epidemiological evidence for future influenza prevention and environmental protection.