Effects of Long-Term Exposure to Air Pollution on the Resurgence of Scarlet Fever in China: A 15-Year Surveillance Study

Abstract

Background: Aimed to investigate the association between the resurgence of scarlet fever and long-term exposure to air pollutants and weather conditions in China. Methods: Data on scarlet fever were from the National Notifiable Disease Reporting System. Air pollutants were from the National Environmental Protection Department, and weather conditions were from the National Meteorological Information Center. A lag non-linear model (DLNM) was used to estimate the excess risk of scarlet fever associated with air pollutants and weather conditions. Findings: 655,039 scarlet fever cases were reported during 2004-18. It started to surge in 2011 (4.7638 per 100 000), and peaked in 2018 (5.6736 per 100 000). The average incidence in 2011-18 was twice that in 2004-10 (rate ratio=2.302; 95% CI: 2.289-2.314; p<0.001]. There was a lowmoderate correlation between scarlet fever and monthly NO2 concentration (r=0.21), sunlight (r=0.28), and wind speed (r=0.24), but the others were weak [PM10 (r=0.13), ozone (r=0.11), and PM2.5 (r=0.05)]. By contrast, it was inversely correlated with monthly relative humidity (RH, r=-0.37), precipitation (r=-0.24) and mean temperature (r=-0.2). A one-unit increment of NO₂ concentration was associated with scarlet fever increased (RR=1.5, 95% CI: 1.35-1.66). The RR was recorded at lag 0 at 42 μg/m3 NO2 concentration (RR=1.15). NO2 pooled estimates varied substantially across China (RR=1.02~4.16), but were higher in northern parts. Interpretation: Long-term exposure to ambient NOâ‚‚ was associated with scarlet fever resurgence, triggered by low RH, temperature, precipitation, and high wind speed and sunshine. Further interventions to reduce NO2 emissions might suppress the resurgence of scarlet fever. Funding Statement: National Science and Technology Major Project of China (Grant no. 2016YFC0202005) and the National Natural Science Foundation of China (Grant no. 41975165, Grant no. 31700320), key epidemiological disciplines of Zhejiang Provincial Health of China, and Shenzhen Science and Technology Innovation Committee (Grant no. JCYJ20160427155352873). Declaration of Interests: The authors declared that they did not have a conflict of interest. Ethics Approval Statement: This study was done according to the principles and guidelines of the Declaration of Helsinki, and was approved by the Research Ethics Committee of the Zhejiang Provincial Center for Disease Control and Prevention. All initial information identifying patients was anonymized in this study.