Influenza incidence and air pollution: Findings from a four-year surveillance study of prefecture-level cities in China

Abstract

BackgroundInfluenza is a serious public health problem, and its prevalence and spread show significant spatiotemporal characteristics. Previous studies have found that air pollutants are linked to an increased risk of influenza. However, the mechanism of influence and the degree of their association have not been determined. This study aimed to determine the influence of the air environment on the spatiotemporal distribution of influenza.MethodsThe kernel density estimation and Getis-Ord Gi* statistic were used to analyze the spatial distribution of the influenza incidence and air pollutants in China. A simple analysis of the correlation between influenza and air pollutants was performed using Spearman's correlation coefficients. A linear regression analysis was performed to examine changes in the influenza incidence in response to air pollutants. The sensitivity of the influenza incidence to changes in air pollutants was evaluated by performing a gray correlation analysis. Lastly, the entropy weight method was used to calculate the weight coefficient of each method and thus the comprehensive sensitivity of influenza incidence to six pollution elements.ResultsThe results of the sensitivity analysis using Spearman's correlation coefficients showed the following ranking of the contributions of the air pollutants to the influenza incidence in descending order: SO2 >NO2 >CO> PM2.5 >O3 >PM10. The sensitivity results obtained from the linear regression analysis revealed the following ranking: CO>NO2 >SO2 >O3 >PM2.5 >PM10. Lastly, the sensitivity results obtained from the gray correlation analysis showed the following ranking: NO2 >CO>PM10 >PM2.5 >SO2 >O3. According to the sensitivity score, the study area can be divided into hypersensitive, medium-sensitive, and low-sensitive areas.ConclusionThe influenza incidence showed a strong spatial correlation and associated sensitivity to changes in concentrations of air pollutants. Hypersensitive areas were mainly located in the southeastern part of northeastern China, the coastal areas of the Yellow River Basin, the Beijing-Tianjin-Hebei region and surrounding areas, and the Yangtze River Delta. The influenza incidence was most sensitive to CO, NO2, and SO2, with the occurrence of influenza being most likely in areas with elevated concentrations of these three pollutants. Therefore, the formulation of targeted influenza prevention and control strategies tailored for hypersensitive, medium-sensitive, low-sensitive, and insensitive areas are urgently needed.

Air Pollution and Influenza: A Systematic Review and Meta-Analysis

“…However, Li et al ( 10 ) did not observe a significant relationship between every 0.1 ug/m 3 increment of CO and influenza, which might be related to regional differences and population specificity. When CO enters the human respiratory tract, CO will form a competitive relationship with O 2 , which will prevent the delivery of oxygen in the body, thus reducing the resistance to influenza virus ( 6 ). However, when we pooled the results of all included original studies and did not stratify by the change in pollutant concentration, the significant association between CO and influenza risk disappeared.…”

“…Air pollutants have become an important global public health issue, in recent years, and a large amount of epidemiological and clinical evidence has shown that air pollutants are associated with respiratory diseases, and their adverse health effects have been well documented ( 5 ). Both brief and prolonged exposure to air pollution raises the risk of morbidity and death from a range of systemic illnesses, which can result in the emergence and spread of influenza ( 6 ). Air pollution can increase the incidence risk of influenza, including diagnosis cases ( 7 ) and outpatient visits ( 8 ).…”

“…Air pollution can increase the incidence risk of influenza, including diagnosis cases ( 7 ) and outpatient visits ( 8 ). In toxicology studies, there are three possible mechanisms that explain why air pollutants increase the incidence of influenza cases, including inflammatory responses, oxidative stress, and mechanical damage ( 6 ). Air pollutants can weaken the body’s immunity, make infected people sick, and carry microorganisms directly to infect people ( 9 ).…”

Investigating the spatiotemporal associations between meteorological conditions and air pollution in the federal state Baden-Württemberg (Germany)

“…For instance, hot spots refer to areas with significantly high values that are surrounded by postal code regions with high values. This method was developed by Luc Anselin 46 and, among others, applied in the context of air pollution 16 , 47 . Several statistics represent the measure of spatial autocorrelation 48 , 49 .…”

“…Most individuals residing in Germany inhabit polluted regions 14 . Air pollution negatively impacts virus-transmitting infections such as influenza 15 , 16 and COVID-19 17 – 19 . Irrespective of which specific health outcome is considered, understanding the interdependencies between environmental variables and the selection of environmental stressors is a key aspect in epidemiological analyses.…”