Severe air pollution links to higher mortality in COVID-19 patients: The “double-hit” hypothesis

• Published in: The Journal of infection 2020-08, Vol.81 (2), p.255-259
• Main Authors: Frontera, Antonio, Cianfanelli, Lorenzo, Vlachos, Konstantinos, Landoni, Giovanni, Cremona, George
• Format: Article
• Language: English
• Subjects: Air Pollutants - adverse effects; Air Pollution - adverse effects; Air Pollution - statistics & numerical data; Betacoronavirus; Coronavirus Infections - epidemiology; Coronavirus Infections - etiology; Coronavirus Infections - mortality; COVID-19; Disease Outbreaks - statistics & numerical data; Hospitalization - statistics & numerical data; Humans; Intensive Care Units - statistics & numerical data; Italy - epidemiology; Nitrogen Dioxide - adverse effects; Pandemics; Particulate Matter - adverse effects; Pneumonia, Viral - epidemiology; Pneumonia, Viral - etiology; Pneumonia, Viral - mortality; Risk Factors; SARS-CoV-2; Severity of Illness Index
• ISSN: 0163-4453; 1532-2742; 1532-2742
• DOI: 10.1016/j.jinf.2020.05.031

•Some regions of the world have higher infection rates from SARS-CoV-2 and with a higher mortality.•These regions have high concentration of air pollutants, especially PM 2.5 and NO2.•Chronic exposure, especially to PM 2.5, correlates with alveolar ACE-2 receptor overexpression leading to more severe COVID-19 infection.•High ambient NO2 may be responsible for the extensive lung injury in COVID-19 pneumonia associated with a worse outcome. In areas of SARS-CoV-2 outbreak worldwide mean air pollutants concentrations vastly exceed the maximum limits. Chronic exposure to air pollutants have been associated with lung ACE-2 over-expression which is known to be the main receptor for SARS-CoV-2. The aim of this study was to analyse the relationship between air pollutants concentration (PM 2.5 and NO2) and COVID-19 outbreak, in terms of transmission, number of patients, severity of presentation and number of deaths. COVID-19 cases, ICU admissions and mortality rate were correlated with severity of air pollution in the Italian regions. The highest number of COVID-19 cases were recorded in the most polluted regions with patients presenting with more severe forms of the disease requiring ICU admission. In these regions, mortality was two-fold higher than the other regions. From the data available we propose a “double-hit hypothesis”: chronic exposure to PM 2.5 causes alveolar ACE-2 receptor overexpression. This may increase viral load in patients exposed to pollutants in turn depleting ACE-2 receptors and impairing host defences. High atmospheric NO2 may provide a second hit causing a severe form of SARS-CoV-2 in ACE-2 depleted lungs resulting in a worse outcome. [Display omitted]