COVID-19 INFECTION, PROGRESSION AND SEVERITY: A CHALLENGE IN THE WINTER SEASON AND PREVENTIVE APPROACH
Coronavirus disease-2019 (COVID-19) is an infectious respiratory disease caused by Severe Acute Respiratory System Coronavirus 2 (SARS-Cov-2). Warm and wet climate reduce the spread of COVID-19 while opposite weather condition prolongs the survival and transmission of viral agents. Particulate matter particularly PM2.5 enhances viral transmission via aerosol. This systemic review was undertaken to describe the association between meteorological condition and air pollutant in winter season and COVID-19 infection. Winter season is associated with dry and cold weather, short sun light and more PM in ambient air. In dry climate exhaled droplets from COVID-19 infected person evaporate to micro droplets and suspended in the air for longer duration. Thus in cold climate a condition with stagnant air and poor ventilation suspended viral particle concentration will increase and enhance the risk of infection. Dry air inhalation leads to decrease the capability of cilia to expel viral aerosols. The concentration of both PM10 and PM2.5 are significantly higher in winter than summer. PM forms condensation nuclei for viral attachment. Besides these fine particles in polluted air induce citrullination of innate antiviral peptide LL-37. Such citrullination blocks the antiviral capacity of LL-37 and exacerbates COVID-19. The lack of sunlight in winter droplets vitamin-D level. Vitamin-D decreases concentration of pro-inflammatory cytokine, IL-6, in lipopolysaccharide-induced inflammation and enhances formation of antiviral peptide LL-37. Thus vit-D deficiency is associated with increased risk of viral infection. The winter season with low humidity, low temperature and more PM in ambient air promotes sustained transmission of SARS-CoV-2. The lack of sunlight in winter droplets vitamin-D level and makes them more susceptible to COVID-19. Thus maintenance of relative humidity within 40% to 60% is important in indoor spaces to restrict transmission. Improving ventilation of public spaces dilute and clear out potentially infectious aerosols. Vit-D supplementation is recommended for people who are at higher risk of vit-D deficiency in COVID-19 pandemic situation.
Keywords: COVID-19, winter, Vitamin-D, Particulate matter.
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